| Station Name |
Months |
Country |
Earliest |
Most Recent |
| O 2 RCH | 159 | United States | Mar 1914 | Aug 1928 |
| O C FISHER DAM | 291 | United States | Dec 1975 | Jul 2002 |
| O NEILL | 1251 | United States | Jan 1893 | Oct 2013 |
| O O RANCH | 522 | United States | Nov 1955 | Aug 2010 |
| O'BRIEN CREEK | 23 | United States | Jul 2008 | Jul 2010 |
| O'LEARY | 451 | Canada | Dec 1960 | Feb 2004 |
| OA | 81 | Federated States of Micronesia | Sep 1956 | May 1966 |
| OAHE DAM | 973 | United States | Sep 1909 | Sep 2003 |
| OAHE-DAM | 862 | United States | Sep 1909 | Dec 1990 |
| OAK BOTTOM CALIFORNIA | 104 | United States | Aug 2001 | May 2010 |
| OAK CITY | 1225 | United States | May 1905 | Sep 2013 |
| OAK CREEK 7WSW | 63 | United States | Jan 2006 | Jul 2011 |
| OAK CREEK ARIZONA | 213 | United States | Jan 1993 | Oct 2013 |
| OAK CREEK CALIFORNIA | 216 | United States | Nov 1994 | Oct 2013 |
| OAK CREEK CANYON | 363 | United States | Jul 1982 | Aug 2013 |
| OAK GROVE CALIFORNIA | 221 | United States | Apr 1995 | Oct 2013 |
| OAK GROVE R S | 148 | United States | Jun 1978 | Oct 1994 |
| OAK HARBOR | 198 | United States | Jan 1984 | Nov 2008 |
| OAK HARBOR | 13 | United States | Mar 1916 | Dec 1917 |
| OAK HILL | 835 | United States | Nov 1941 | Oct 2012 |
| OAK HILL | 34 | United States | Jan 1894 | Nov 1896 |
| OAK ISLAND | 27 | United States | Nov 1943 | Mar 1946 |
| OAK KNOLL CALIFORNIA | 285 | United States | Jan 1989 | Oct 2013 |
| OAK MOUNTAIN CALIFORNIA | 155 | United States | Sep 1991 | Oct 2013 |
| OAK MTN STATE PARK 2 N | 53 | United States | Nov 1998 | Aug 2007 |
| OAK OPENING CALIFORNIA | 200 | United States | Jul 1996 | Oct 2013 |
| OAK PARK - CARLOW | 61 | Ireland | Aug 2008 | Oct 2013 |
| OAK RIDGE | 201 | United States | Jun 1947 | Apr 1964 |
| OAK RIDGE | 57 | United States | Jul 1895 | Apr 1901 |
| OAK RIDGE ASOS | 789 | United States | Jan 1948 | Oct 2013 |
| OAK RIDGES | 628 | Canada | Jun 1918 | Nov 1979 |
| OAK VALLEY | 22 | Canada | Jan 2004 | Sep 2006 |
| OAKBANK | 418 | Canada | Jan 1890 | Jun 1931 |
| OAKBANK | 415 | Canada | Jan 1890 | Jun 1931 |
| OAKDALE | 1497 | United States | Jan 1888 | Oct 2013 |
| OAKDALE ALLEN PARISH AP | 94 | United States | Apr 2005 | Oct 2013 |
| OAKDALE WOODWARD DAM | 550 | United States | Apr 1918 | Dec 1967 |
| OAKES 2 S | 943 | United States | Jan 1929 | Oct 2013 |
| OAKES MUNI ARPT | 23 | United States | Jun 2011 | May 2013 |
| OAKEY AERODRO | 477 | Australia | May 1973 | Oct 2013 |
| OAKFIELD | 327 | United States | Jan 1893 | Apr 1920 |
| OAKLAND | 26 | United States | Jul 1905 | Dec 1907 |
| OAKLAND | 16 | United States | Jun 2012 | Oct 2013 |
| OAKLAND (BERTH 34) | 23 | United States | Oct 2011 | Oct 2013 |
| OAKLAND 1 SE | 1346 | United States | May 1893 | Oct 2013 |
| OAKLAND 2 SW | 1071 | United States | Jan 1919 | Oct 2013 |
| OAKLAND CITY HALL | 54 | United States | May 1949 | Feb 1954 |
| OAKLAND GARRETT COUNTY AP | 78 | United States | Nov 2006 | Oct 2013 |
| OAKLAND NAS | 31 | United States | Jun 1949 | Oct 1954 |
| OAKLAND NORTH CALIFORNIA | 227 | United States | Jul 1992 | Oct 2013 |
| OAKLAND SOUTH CALIFORNIA | 1199 | United States | Mar 1897 | Oct 2013 |
| OAKLAND-1SE | 1079 | United States | Apr 1893 | Dec 1990 |
| OAKLAND/METROP. OAKLAND INT., CA. | 993 | United States | Jan 1931 | Oct 2013 |
| OAKLANDON GEIST RESERVOIR | 659 | United States | Jun 1937 | Jul 1998 |
| OAKLEY | 1438 | United States | Jun 1893 | Sep 2013 |
| OAKLEY 19 SSW | 96 | United States | Nov 2005 | Oct 2013 |
| OAKLEY 4 W | 1078 | United States | Feb 1920 | Oct 2013 |
| OAKLEY EXP STA | 452 | United States | Jul 1970 | Feb 2011 |
| OAKMULGEE ALABAMA | 155 | United States | Jul 1998 | Mar 2013 |
| OAKNER | 425 | Canada | Sep 1965 | Oct 2007 |
| OAKPOINT MARINE | 187 | Canada | Sep 1996 | Oct 2013 |
| OAKRIDGOAKRIDGE FISHE HATCHERY | 1014 | United States | Aug 1923 | Sep 2013 |
| OAKS | 33 | United States | May 1915 | Oct 1919 |
| OAKVILLE | 895 | United States | May 1916 | Dec 1997 |
| OAKVILLE 1 WNW | 93 | United States | Apr 1906 | Jun 1914 |
| OAKVILLE SOUTHEAST WPCP | 515 | Canada | Jun 1958 | Sep 2006 |
| OAKWOOD 3 SW | 736 | United States | Oct 1909 | Sep 1975 |
| OAKWOOD 7 NW | 13 | United States | Oct 1980 | Nov 1981 |
| OASIS | 284 | United States | Jun 1987 | Jun 2012 |
| OASIS 5 S | 19 | United States | Oct 1985 | Apr 1987 |
| OASIS FISHING LODGE | 19 | United States | Aug 1954 | Nov 1956 |
| OASIS FLORIDA | 122 | United States | Apr 2002 | Oct 2013 |
| OASIS RANGER STN | 419 | United States | Jun 1978 | Oct 2013 |
| OATLANDS POST OFFICE | 413 | Australia | Jan 1957 | Jul 1993 |
| OAXACA/XOXOCOTLAN | 990 | Mexico | May 1922 | Oct 2013 |
| OAZIS | 26 | Antarctica | Jan 1956 | Oct 1958 |
| OBA | 116 | Canada | Mar 1926 | Aug 1946 |
| OBAN | 272 | United Kingdom | Sep 1978 | Oct 2013 |
| OBAR | 488 | United States | Jan 1926 | Jun 1968 |
| OBARI | 134 | Libya | Sep 1993 | Mar 2011 |
| OBARSIA LOTRULUI | 147 | Romania | Jan 1985 | Sep 2002 |
| OBAYLAH (AUT) | 7 | Saudi Arabia | May 1983 | Dec 1984 |
| OBBIA | 239 | Somalia | Jan 1925 | Dec 1958 |
| OBERGURGL | 131 | Austria | Jul 2002 | Oct 2013 |
| OBERLIN | 1588 | United States | Jan 1854 | May 2009 |
| OBERLIN | 1196 | United States | May 1913 | Oct 2013 |
| OBERLIN FIRE TOWER | 717 | United States | Nov 1953 | Oct 2013 |
| OBERLIN-1E | 924 | United States | May 1913 | Dec 1990 |
| OBERON (JENOLAN CAVES ROAD) | 154 | Australia | Sep 1989 | Jul 2005 |
| OBERON (JENOLAN CAVES) | 653 | Australia | Jan 1907 | Apr 1973 |
| OBERON (SPRINGBANK) | 250 | Australia | Jan 1965 | Sep 2013 |
| OBERPFAFFENHOFEN | 76 | Germany | May 2007 | Oct 2013 |
| OBERPFAFFENHOFEN GERMANY AD | 33 | Germany | Sep 1946 | Jul 1949 |
| OBERSCHLEISSHEIM | 87 | Germany | Jan 1973 | Mar 1981 |
| OBERSTDORF | 924 | Germany | Jan 1936 | Jul 2013 |
| OBERTAUERN | 254 | Austria | Jun 1990 | Oct 2013 |
| OBERVELLACH | 154 | Austria | Mar 1991 | Oct 2013 |
| OBIDJUAN | 190 | Canada | Sep 1923 | Jun 1950 |
| OBIHIRO AIRPORT | 487 | Japan | Jan 1973 | Oct 2013 |
| OBIHIRO-ON-HOKKAIDO | 1417 | Japan | Jan 1894 | Oct 2013 |
| OBIR | 1147 | Austria | Jan 1848 | Jun 1944 |
| OBJACEVO | 327 | Russia | Jun 1975 | Oct 2013 |
| OBLUCE | 593 | Russia | Mar 1953 | Oct 2013 |
| OBO | 462 | Central African Republic | Apr 1954 | Mar 2003 |
| OBOJAN' | 14 | Russia | Aug 2012 | Oct 2013 |
| OBRESTAD | 156 | Norway | Mar 1986 | Oct 2013 |
| OBRESTAD FYR | 582 | Norway | Jan 1954 | Aug 2013 |
| OBS MET NACI | 557 | Colombia | Mar 1941 | Feb 1993 |
| OBSIDIAN 3 SSE | 504 | United States | Jun 1919 | Jul 1962 |
| OCALA | 1499 | United States | Jan 1835 | Oct 2013 |
| OCALA 2 NE | 282 | United States | Jan 1941 | Jan 1966 |
| OCALA INTL J TAYLOR | 527 | United States | Jan 1944 | Oct 2013 |
| OCALA JIM TAYLOR FLD | 7 | United States | May 2005 | Dec 2005 |
| OCATE 2 NW | 635 | United States | Jan 1893 | Sep 2013 |
| OCCIDENTAL | 122 | United States | Apr 1999 | Oct 2013 |
| OCEAN CITY INLET | 52 | United States | Jun 2009 | Oct 2013 |
| OCEAN CITY MUNI AP | 589 | United States | Jan 1907 | Oct 2013 |
| OCEAN CREST PIER | 63 | United States | May 2007 | Oct 2013 |
| OCEAN FALLS,BC | 732 | Canada | Jan 1924 | Nov 1986 |
| OCEAN IS/BANABA | 940 | Kiribati | Sep 1904 | Dec 1990 |
| OCEANA 2 SE | 263 | United States | Apr 1899 | Oct 2013 |
| OCEANA NAS | 780 | United States | Mar 1945 | Oct 2013 |
| OCEANSIDE | 179 | United States | Sep 1994 | Dec 2009 |
| OCEANSIDE CAA AP | 843 | United States | Jul 1910 | Sep 2013 |
| OCEANSIDE HARBOR | 8 | United States | Jul 1987 | Feb 1992 |
| OCEANSIDE MUNICIPAL AP | 172 | United States | Jun 1999 | Oct 2013 |
| OCEMCIRI | 59 | Georgia | Feb 1970 | Aug 1991 |
| OCHAKOV | 120 | Ukraine | Jan 1970 | Apr 2004 |
| OCHIAI (DOLINSK) | 497 | Russia | Feb 1908 | Dec 1950 |
| OCHILTREE MIOCENE | 351 | Canada | Jan 1963 | Aug 2003 |
| OCHOA | 242 | United States | May 1991 | Sep 2013 |
| OCHOCO DAM | 42 | United States | Aug 1948 | Oct 2013 |
| OCHOCO MEADOWS | 283 | United States | Jul 1989 | Oct 2013 |
| OCHOCO RANGER STATION | 863 | United States | Sep 1936 | Oct 2013 |
| OCHOPEE FLORIDA | 296 | United States | May 1987 | Oct 2013 |
| OCHRE RIVER | 298 | Canada | Jun 1970 | Sep 2005 |
| OCHRE RIVER,MA | 217 | Canada | Jun 1970 | Dec 1989 |
| OCILLA WTP | 70 | United States | Apr 2002 | Sep 2009 |
| OCNA SUGATAG | 573 | Romania | Jan 1961 | Dec 2009 |
| OCNA SUGATAG | 276 | Romania | Apr 1983 | Oct 2013 |
| OCONALUFTEE | 635 | United States | Nov 1958 | Oct 2013 |
| OCONEE #1 GEORGIA | 127 | United States | Sep 2001 | Oct 2013 |
| OCONEE CO RGNL | 145 | United States | Sep 2001 | Oct 2013 |
| OCONOMOWOC | 870 | United States | Jan 1893 | Oct 2013 |
| OCONTO | 591 | United States | Jun 1962 | Sep 2013 |
| OCONTO 4 W | 1445 | United States | Feb 1891 | Oct 2013 |
| OCONTO-4W | 1167 | United States | Dec 1890 | Nov 1990 |
| OCOTILLO WELLS 2W | 118 | United States | Mar 1932 | Sep 2013 |
| OCRACOKE | 381 | United States | Jun 1957 | Oct 2013 |
| OCTA (1) | 61 | United States | Jun 1921 | Jul 1926 |
| OCTORARO LAKE | 413 | United States | Feb 1978 | Sep 2013 |
| OCUSSI====PORTUGUESE TIM | 59 | East Timor | Jan 1956 | Nov 1960 |
| ODATE-NOSHIRO AIRPORT | 174 | Japan | Apr 1999 | Oct 2013 |
| ODDUR | 273 | Somalia | Jan 1922 | Dec 1958 |
| ODEBOLT | 198 | United States | Nov 1897 | Nov 1914 |
| ODEBYN | 31 | Sweden | Jan 1961 | Mar 1964 |
| ODELL LAKE LAND PAN | 646 | United States | Jun 1945 | Oct 2013 |
| ODELL LAKE WATER PAN | 150 | United States | Jun 1945 | May 1959 |
| ODEMIS | 360 | Turkey | Jan 1961 | Dec 1990 |
| ODEN 1 SE | 242 | United States | Jan 1927 | Mar 1951 |
| ODEN ARKANSAS | 171 | United States | Jul 1998 | Oct 2013 |
| ODENSE/BELDRINGE | 487 | Denmark | Jan 1973 | Oct 2013 |
| ODESSA | 2067 | Ukraine | Jan 1821 | Oct 2013 |
| ODESSA | 1318 | United States | Feb 1903 | Aug 2013 |
| ODESSA | 191 | United States | Oct 1950 | Oct 2013 |
| ODESSA | 107 | Canada | Aug 1971 | Dec 1981 |
| ODESSA | 67 | United States | May 1937 | Dec 1942 |
| ODESSA SCHLEMEYER FLD | 179 | United States | Dec 1998 | Oct 2013 |
| ODESSKOE | 559 | Russia | Feb 1950 | Oct 2013 |
| ODIENNE IVOR ODIE | 851 | Cote D'Ivoire | Jan 1941 | Sep 2013 |
| ODIHAM | 484 | United Kingdom | Jan 1973 | Oct 2013 |
| ODORHEIUL SECUIESC | 183 | Romania | May 1983 | Sep 2002 |
| OE-CUSSIE | 12 | East Timor | Dec 1996 | Mar 1999 |
| OEDUM | 16 | Denmark | May 2012 | Oct 2013 |
| OEHRINGEN | 383 | Germany | Jan 1949 | Dec 2011 |
| Oelands Norra Udde | 1909 | Sweden | Jul 1854 | Oct 2013 |
| OELRICHS | 1383 | United States | Jan 1893 | Sep 2013 |
| OELWEIN 2 S | 1054 | United States | May 1923 | Jul 2013 |
| OELWEIN MUNI AP | 202 | United States | May 1995 | Oct 2013 |
| OESTERSUND FROSON | 1834 | Sweden | Sep 1860 | Oct 2013 |
| OFFENBACH-M | 63 | Germany | Jul 1995 | Mar 2001 |
| OFFENBACH-WETTERPARK | 93 | Germany | Oct 2005 | Jul 2013 |
| OFUNATO | 597 | Japan | Aug 1963 | Oct 2013 |
| OGALLALA | 1066 | United States | Mar 1894 | Oct 2013 |
| OGALLALA SEARLE FLD AP | 198 | United States | Mar 1997 | Oct 2013 |
| OGDEN | 152 | United States | Jul 1894 | Sep 1959 |
| OGDEN | 33 | United States | Jan 2011 | Oct 2013 |
| OGDEN DUNES | 448 | United States | Oct 1951 | Apr 1989 |
| OGDEN HILL AAF | 836 | United States | Oct 1941 | Oct 2013 |
| OGDEN HINKLEY AIRPORT | 1363 | United States | Jan 1893 | Oct 2013 |
| OGDEN NE BENCH | 34 | United States | Dec 2010 | Oct 2013 |
| OGDEN SUGAR FACTORY | 988 | United States | Sep 1924 | May 2009 |
| OGDEN-PIONEER-P-H | 1418 | United States | Feb 1870 | Dec 1990 |
| OGDENSBURG 4 NE | 1340 | United States | Jan 1893 | Oct 2013 |
| OGDENSBURG INTL | 138 | United States | Feb 1984 | Oct 2013 |
| OGDENSBURG-4NE | 1176 | United States | Jan 1838 | Dec 1990 |
| OGESTAD | 573 | Sweden | Jan 1961 | Jul 2009 |
| OGILVIE RIVER | 267 | Canada | Aug 1971 | Oct 2006 |
| OGILVIE RIVER,YT | 167 | Canada | Aug 1971 | Nov 1989 |
| OGIZTAU | 84 | Kazakhstan | Dec 1978 | Nov 1991 |
| OGLALA 1 S | 174 | United States | Dec 1998 | Oct 2013 |
| OGLIUGA ALASKA | 13 | United States | Apr 1943 | Jun 1944 |
| OGORON | 263 | Russia | Feb 1956 | Jun 1993 |
| OGRTSOVO | 108 | Russia | Aug 2004 | Oct 2013 |
| OGRYDA | 101 | Turkmenistan | Jan 1959 | Feb 1995 |
| OGULIN | 330 | Croatia | Jun 1975 | Oct 2013 |
| OGURCOVO | 632 | Russia | Jan 1958 | Sep 2012 |
| OHA | 299 | Russia | May 1937 | Oct 2013 |
| OHAGAMUTE | 22 | United States | Apr 1936 | May 1938 |
| OHAKEA | 234 | New Zealand | Mar 1954 | Oct 1991 |
| OHANSK | 516 | Russia | Jan 1969 | Oct 2013 |
| OHARA BAR | 14 | United States | Dec 1909 | Feb 1913 |
| OHE'O 258.6 | 174 | United States | Nov 1998 | Sep 2013 |
| OHIO GULCH IDAHO | 277 | United States | Jul 1990 | Oct 2013 |
| OHIO STATE UNIVERSI | 363 | United States | Aug 1982 | Oct 2013 |
| OHIO UNIVERSITY SNY | 75 | United States | Jun 2007 | Oct 2013 |
| OHIOVILLE | 30 | United States | Jan 1924 | Nov 1927 |
| OHONY | 158 | Russia | Jan 1959 | Oct 2013 |
| OHOTSKIJPEREVOZ | 330 | Russia | Jan 1959 | Oct 2013 |
| OHRID | 413 | Macedonia | May 1975 | Oct 2013 |
| OHRID-AERODROME | 224 | Macedonia | Jul 1991 | Jul 2013 |
| OHRINGEN | 794 | Germany | May 1947 | Jul 2013 |
| OIAPOQUE | 60 | Brazil | May 1987 | Oct 2013 |
| OIL CITY | 69 | Canada | Dec 1953 | Nov 1959 |
| OIL CITY 3E | 41 | United States | May 2005 | Jul 2009 |
| OIL PLATFORM/EAST B | 27 | United States | Jan 2010 | Oct 2013 |
| OIL PLATFORM/GUNNIS | 38 | United States | Jan 2010 | Oct 2013 |
| OIL PLATFORM/INDEPE | 38 | United States | Jan 2010 | Sep 2013 |
| OIL PLATFORM/INNOVA | 36 | United States | Jan 2010 | Aug 2013 |
| OIL PLATFORM/MAGNOLI | 41 | United States | Feb 2010 | Oct 2013 |
| OIL PLATFORM/SHIP S | 39 | United States | Jan 2010 | Sep 2013 |
| OIL SHALE MINE | 56 | United States | Feb 1947 | Nov 1951 |
| OIL SPRINGS | 68 | Canada | Oct 1960 | Mar 1967 |
| OIL WELL ROAD E P | 78 | United States | Nov 1967 | Jul 1974 |
| OILTON | 72 | United States | Nov 1964 | Jan 1971 |
| OITA | 1519 | Japan | Jan 1887 | Oct 2013 |
| OITA AIRPORT | 489 | Japan | Jan 1973 | Oct 2013 |
| OJAI | 1279 | United States | May 1905 | Sep 2013 |
| OJAI CALIFORNIA | 145 | United States | Jul 2000 | Dec 2012 |
| OJEBRO | 168 | Sweden | Jan 1961 | Sep 1977 |
| OJIBWAY MICHIGAN | 113 | United States | May 2002 | Oct 2013 |
| OJIKA ISLAND | 59 | Japan | Dec 1992 | Jan 1999 |
| OJINAGA | 361 | Mexico | Jun 1923 | Nov 1998 |
| OJITLAN, OAXACA | 426 | Mexico | Dec 1947 | Dec 1983 |
| OJMJAKON | 988 | Russia | Jan 1930 | Oct 2013 |
| OJO CALIENTE | 404 | Mexico | Apr 1937 | Oct 1984 |
| OK FALLS MCLEAN CRK | 92 | Canada | Dec 1982 | Mar 1991 |
| OKA | 752 | Canada | Sep 1937 | Nov 2011 |
| OKANAGAN CENTRE | 924 | Canada | Jan 1926 | Sep 2013 |
| OKANAGAN MISSION TOZER | 53 | Canada | Jul 1987 | Jan 1992 |
| OKANOGAN | 279 | United States | Mar 1926 | Jan 1950 |
| OKAUKUEJO | 21 | Namibia | Mar 2008 | Oct 2013 |
| OKAY | 794 | United States | Jun 1915 | Sep 1992 |
| OKAYAMA | 1442 | Japan | Jan 1891 | Oct 2013 |
| OKAYAMA AIRPORT | 480 | Japan | Jan 1973 | Oct 2013 |
| OKEECHOBEE | 676 | United States | Jul 1945 | Dec 2010 |
| OKEECHOBEE | 76 | United States | Feb 2007 | Oct 2013 |
| OKEECHOBEE 9 W | 18 | United States | Oct 1971 | Mar 1973 |
| OKEECHOBEE INTOWN | 12 | United States | Mar 2011 | Jun 2012 |
| OKEECHOBEE NEAR | 208 | United States | Feb 1918 | May 1945 |
| OKEENE | 1237 | United States | May 1903 | Feb 2011 |
| OKEMAH | 1191 | United States | May 1912 | Sep 2012 |
| OKETO | 230 | United States | Jan 1931 | Sep 1950 |
| OKHA | 103 | Russia | Sep 2004 | May 2013 |
| OKHOTSK | 1302 | Russia | Oct 1890 | Oct 2013 |
| OKINAWA RYUKYU IS/DRAKE FLD | 8 | Japan | May 1945 | Dec 1945 |
| OKINAWA RYUKYU IS/YONTAN AB | 30 | Japan | Jun 1951 | Jan 1954 |
| OKINAWA RYUKYU ISLAN | 32 | Japan | Jun 1951 | Jan 1954 |
| OKINAWA/RYUKYU ISLANDS | 213 | Japan | May 1949 | Mar 1968 |
| OKINOERABU | 533 | Japan | May 1969 | Oct 2013 |
| OKLAHOMA CITY PENN AVE | 537 | United States | Jan 1914 | Jan 1975 |
| OKLAHOMA CITY POST AP | 203 | United States | Aug 1996 | Oct 2013 |
| OKLAHOMA CITY TINKER AAF | 819 | United States | Jan 1943 | Oct 2013 |
| OKLAHOMA CITY, OK | 1264 | United States | Jan 1900 | May 2005 |
| OKLAHOMA CITY/PAGE | 52 | United States | Apr 2009 | Oct 2013 |
| OKLAHOMA CITY/W. ROGERS WORLD, OK. | 1475 | United States | Nov 1890 | Oct 2013 |
| OKLAHOMA CITY/WILEY | 324 | United States | Sep 1985 | Oct 2013 |
| OKLEE | 305 | United States | Sep 1967 | Jun 1996 |
| OKMULGEE RGNL | 109 | United States | Jun 2004 | Oct 2013 |
| OKMULGEE WATER WORKS | 1181 | United States | Sep 1903 | Oct 2011 |
| OKMULGEE-WATER-WORKS | 992 | United States | Sep 1903 | Dec 1990 |
| OKOLONA | 402 | United States | May 1891 | Mar 1927 |
| OKOTOKS | 483 | Canada | Mar 1913 | Sep 2013 |
| OKSOEY FYR | 1484 | Norway | Jan 1890 | Aug 2013 |
| OKSOY FYR | 487 | Norway | Jan 1973 | Oct 2013 |
| OKSYWIE | 135 | Poland | Jun 2002 | Oct 2013 |
| OKTIABR'SKAYA | 754 | Russia | Jan 1909 | Oct 2010 |
| OKTIABRSKAYA | 383 | Russia | Feb 1949 | Nov 1989 |
OKTJABR| 1589 | Russia | Jan 1881 | Oct 2013 | |
| OKTJABRSKIJ GORODOK | 56 | Russia | Feb 2009 | Oct 2013 |
| OKTJABRSKIJ PRIISK | 161 | Russia | Jun 1956 | Mar 1991 |
| OKTJABRSKOE | 616 | Russia | Oct 1952 | Jul 2013 |
| OKTYABR SKOYE | 881 | Russia | Jan 1936 | Aug 2012 |
| OKULOVSKAYA | 51 | Russia | Aug 1984 | Jul 1991 |
| OKUNEV NOS | 174 | Russia | Jul 1961 | Oct 2013 |
| OKUSHIRI ISLAND | 267 | Japan | Jun 1975 | Feb 1999 |
| OLA | 662 | Russia | Jan 1955 | Aug 2012 |
| OLA | 71 | Russia | Jan 1969 | Jul 1976 |
| OLA 4 S | 896 | United States | Oct 1896 | Dec 2012 |
| OLAA 92 | 683 | United States | Jan 1905 | Dec 1962 |
| OLAA KURTISTOWN | 143 | United States | Feb 1906 | Jul 1921 |
| OLAF KNOLLS ARIZONA | 326 | United States | Jun 1985 | Oct 2013 |
| OLALLIE MEADOWS | 263 | United States | Sep 1990 | Oct 2013 |
| OLANDS SODRA GRUND | 88 | Sweden | Sep 1981 | Sep 1993 |
| OLANDS SODRA UDDE | 628 | Sweden | Jan 1961 | Oct 2013 |
| OLANDSBRON LAG | 139 | Sweden | Jul 2001 | Oct 2013 |
| OLANDSBRON_V | 180 | Sweden | Apr 1996 | Dec 2011 |
| OLATHE 3 E | 1342 | United States | May 1893 | Sep 2009 |
| OLATHE JOHNSON CO EXEC AP | 206 | United States | Jul 1996 | Oct 2013 |
| OLATHE JOHNSON CO INDUSTRIAL | 703 | United States | Mar 1945 | Oct 2013 |
| OLATHE-3E | 1201 | United States | Jan 1864 | Dec 1990 |
| OLAVARRIA AERO | 57 | Argentina | Apr 1992 | Sep 1997 |
| OLBIA/COSTA SMERALD | 698 | Italy | Jan 1951 | Oct 2013 |
| OLCOTT HARBOR | 70 | United States | Nov 2007 | Oct 2013 |
| OLD BATTLE | 231 | United States | Nov 1986 | Oct 2013 |
| OLD CROW | 418 | Canada | Nov 1977 | Oct 2013 |
| Old Crow A | 576 | Canada | Sep 1951 | Sep 1999 |
| OLD CROW AIRPORT | 455 | Canada | Oct 1951 | Jan 2013 |
| OLD CROW RCS, YT | 195 | Canada | May 1996 | Oct 2013 |
| OLD EDGERTON | 306 | United States | Apr 1970 | Jan 1996 |
| OLD FAITHFUL | 603 | United States | May 1904 | Oct 2013 |
| OLD FERRY ISLAND | 34 | United States | Aug 2004 | Dec 2008 |
| OLD FORGE | 805 | United States | Dec 1907 | Oct 2013 |
| OLD FORT LARAMIE | 282 | United States | Dec 1989 | Oct 2013 |
| OLD FT AG 3 W | 31 | United States | Jan 2011 | Sep 2013 |
| OLD GLORY MOUNTAIN | 272 | Canada | Nov 1944 | Dec 1967 |
| OLD HARBOR | 32 | United States | Apr 1968 | May 1971 |
| OLD HICKORY DAM | 38 | United States | Apr 1966 | Oct 2013 |
| OLD HICKORY WSMO | 272 | United States | Nov 1990 | Oct 2013 |
| OLD MAN | 21 | United States | Feb 1975 | Oct 1976 |
| OLD MAN | 11 | United States | Nov 1974 | Oct 1975 |
| OLD MISSION 3 SSW | 786 | United States | Mar 1894 | Oct 2013 |
| OLD RIVER LOCK | 285 | United States | Mar 1965 | Dec 1988 |
| OLD RUTH | 632 | United States | Jun 1958 | Oct 2013 |
| OLD TOWN | 19 | United States | Jul 1918 | Aug 1920 |
| OLD TOWN 2 W | 561 | United States | Jan 1921 | Oct 2013 |
| OLD TOWN FAA AIRPORT | 284 | United States | Jun 1948 | Jan 1972 |
| OLD WOMEN CREEK | 68 | United States | Feb 2008 | Oct 2013 |
| OLDEN | 228 | United States | Jan 1893 | Dec 1912 |
| OLDENBURG | 475 | Germany | Jan 1973 | Sep 2012 |
| OLDFIELD | 357 | United States | Jul 1963 | Dec 2004 |
| OLDS | 1028 | Canada | May 1914 | Jun 2013 |
| OLDS AGDM | 112 | Canada | Mar 2004 | Oct 2013 |
| OLDS AGDM, ALTA | 107 | Canada | Nov 2004 | Oct 2013 |
| OLEAN | 34 | United States | May 1980 | Oct 2013 |
| OLEKMINSK | 1457 | Russia | Aug 1882 | Oct 2013 |
| OLEN'YA RECHKA | 286 | Russia | Jan 1960 | Oct 2013 |
| OLENEK | 915 | Russia | Jul 1935 | Oct 2013 |
| OLENJA RECHKA | 923 | Russia | Jul 1931 | Sep 2012 |
| OLEVSK | 91 | Ukraine | Nov 1970 | Aug 1984 |
| OLEVSK | 32 | Ukraine | Jan 2000 | May 2004 |
| OLGA 2 SE | 1459 | United States | Jul 1891 | Sep 2013 |
| OLGAING | 62 | Uzbekistan | Feb 1976 | Apr 1997 |
| OLHA | 52 | Canada | Dec 1966 | Jun 1971 |
| OLIKTOK POW 2 | 300 | United States | Aug 1957 | Aug 1988 |
| OLIN | 484 | United States | Mar 1898 | Jun 1941 |
| OLINDA (S) | 24 | United States | Aug 1912 | Apr 1917 |
| OLIPHANT\ONT | 25 | Canada | Jul 1992 | Nov 1994 |
| OLIVE BRANCH | 351 | United States | Nov 1941 | Dec 2004 |
| OLIVE BRANCH | 177 | United States | Mar 1983 | Feb 1999 |
| OLIVE BRANCH | 171 | United States | Apr 1998 | Oct 2013 |
| OLIVE BRANCH AP | 92 | United States | Jan 2005 | Oct 2013 |
| OLIVE HILL 5NE | 86 | United States | Aug 2006 | Oct 2013 |
| OLIVE LAKE | 74 | United States | Nov 1940 | Aug 1947 |
| OLIVER | 803 | Canada | Jun 1938 | Jul 2008 |
| OLIVER AGDM | 113 | Canada | Jan 2004 | Oct 2013 |
| OLIVER AGDM, ALTA | 110 | Canada | Jun 2004 | Oct 2013 |
| OLIVER STP | 832 | Canada | Feb 1924 | Jan 2013 |
| OLIVER TREE NURSERY | 247 | Canada | Jun 1972 | Dec 1993 |
| OLIVET | 299 | United States | Mar 1892 | Feb 1919 |
| OLIVIA RGNL AP | 110 | United States | Jun 2004 | Oct 2013 |
| OLIVIA-3SE | 1203 | United States | Mar 1885 | Dec 1990 |
| OLLA | 339 | United States | Jan 1970 | Jan 2009 |
| OLMSTEAD P H | 316 | United States | Mar 1977 | Aug 2003 |
| OLNEY | 618 | United States | Dec 1955 | Jul 2011 |
| OLNEY | 573 | United States | Jun 1962 | Oct 2013 |
| OLNEY 2 S | 1402 | United States | Jan 1893 | Oct 2013 |
| OLNEY NOBLE AP | 134 | United States | Jul 2002 | Oct 2013 |
| OLNEY-2S | 1206 | United States | Jul 1887 | Dec 1990 |
| OLNEYVILLE | 7 | United States | May 1893 | Nov 1893 |
| OLONEC | 148 | Russia | Jan 1959 | Oct 2013 |
| OLONESTY | 95 | Moldova | Nov 1970 | Dec 1981 |
| OLONGAPO | 64 | Philippines | Feb 1950 | Jul 1955 |
| OLOVARRIA_AERO ARGENTI | 23 | Argentina | Jan 1999 | Feb 2004 |
| OLOVJANNAJA | 571 | Russia | Feb 1948 | Oct 2013 |
| OLPENITZ (AUT) | 83 | Germany | Aug 1975 | Nov 1992 |
| OLSENS BRIDGE (MORWELL RIVER P | 421 | Australia | Dec 1951 | Jan 1997 |
| OLSIA SARDINIA | 56 | Italy | Jan 1966 | Aug 1975 |
| OLSZTYN | 752 | Poland | Jan 1951 | Oct 2013 |
| OLTENITA | 159 | Romania | Feb 1985 | Sep 2002 |
| OLTON | 578 | United States | May 1942 | Oct 2013 |
| OLTU | 228 | Turkey | Aug 1967 | Dec 1990 |
| OLUSTEE FLORIDA | 109 | United States | Mar 2003 | Oct 2013 |
| OLVINGSTORP | 77 | Sweden | Jan 1961 | Jun 1967 |
| OLYMPIA FOREST HQ | 64 | United States | Jan 1943 | Sep 1952 |
| OLYMPIA MUNICIPAL ARPT | 1483 | United States | Jan 1890 | Oct 2013 |
| OLYMPIA, WA | 1252 | United States | Jan 1900 | Jul 2004 |
| OLYMPIC DAM AERODROME | 131 | Australia | Oct 2001 | Oct 2013 |
| OMAEZAKI | 981 | Japan | Jan 1932 | Oct 2013 |
| OMAHA 2 W | 82 | United States | Sep 1997 | Jun 2004 |
| OMAHA/EPPLEY FIELD | 474 | United States | May 1974 | Oct 2013 |
| OMAHA/OFFUTT AFB, NE. | 899 | United States | Aug 1905 | Oct 2013 |
| OMAK AIRPORT | 1195 | United States | Dec 1909 | Oct 2013 |
| OMEO COMPARISON | 1584 | Australia | Apr 1879 | Oct 2013 |
| OMER | 272 | United States | Feb 1897 | Jun 1925 |
| OMIDYEH-AGHAJARI | 132 | Iran | Feb 2001 | Oct 2013 |
| OMINATO | 3 | Japan | Mar 1989 | Feb 1990 |
| OMINATO AB | 486 | Japan | Jan 1973 | Oct 2013 |
| OMNOGOVI (UMNU-GOBI) UVS | 603 | Mongolia | Jan 1963 | Oct 2013 |
| OMOE FYR | 375 | Denmark | Jan 1973 | Oct 2013 |
| OMOLON | 805 | Russia | May 1944 | Oct 2013 |
| OMPAH | 141 | Canada | Aug 1994 | Nov 2006 |
| OMPAH-SEITZ | 140 | Canada | Aug 1994 | Nov 2006 |
| OMPS | 109 | United States | Nov 1963 | May 1973 |
| OMSK | 1508 | Russia | Jul 1887 | Oct 2013 |
| OMSUKCHAN | 88 | Russia | Jul 1961 | Oct 2013 |
| OMU | 834 | Japan | Jan 1943 | Oct 2013 |
| ONA HUSOY | 1748 | Norway | Jan 1868 | Oct 2013 |
| ONAHAMA | 1240 | Japan | May 1910 | Oct 2013 |
| ONANCOCK | 4 | United States | Mar 1912 | Aug 1912 |
| ONATCHIWAY, QUE | 618 | Canada | Jul 1920 | Dec 2010 |
| ONAWA 3 NW | 1316 | United States | Mar 1899 | Oct 2011 |
| ONAWAY 12 S | 599 | United States | Dec 1900 | May 1955 |
| ONAWAY STATE PARK | 1001 | United States | May 1928 | Oct 2013 |
| ONCESTI | 152 | Romania | May 1983 | Nov 1999 |
| ONDAL INDIA | 30 | India | Jun 1943 | Dec 1945 |
| ONDANGWA | 72 | Namibia | Jun 1988 | Oct 2013 |
| ONDANGWA | 62 | Namibia | Jan 2005 | Oct 2013 |
| ONDO | 120 | Nigeria | Jan 1991 | Dec 2000 |
| ONDORHAAN (UNDERHAN) HENTIY | 920 | Mongolia | Sep 1936 | Oct 2013 |
| ONEFOUR CDA, ALTA | 247 | Canada | Sep 1991 | Oct 2013 |
| ONEGA | 1486 | Russia | Feb 1887 | Oct 2013 |
| ONEIDA | 605 | United States | Dec 1959 | Sep 2013 |
| ONEIDA | 89 | United States | Jul 2004 | May 2013 |
| ONEILL MUNI AP | 9 | United States | Jan 2005 | Dec 2005 |
| ONEONTA | 1107 | United States | Sep 1894 | Sep 2013 |
| ONEONTA STATE UNIV | 1370 | United States | Sep 1894 | Oct 2013 |
| ONG-YEM | 90 | Vietnam | Dec 1898 | Jul 1909 |
| ONGERUP | 558 | Australia | Aug 1966 | Sep 2013 |
| ONGOLE | 49 | India | Sep 2009 | Oct 2013 |
| ONGUDAJ | 347 | Russia | Jan 1960 | Dec 1994 |
| ONI | 69 | Georgia | Jan 1959 | Apr 1991 |
| ONIDA 4 NW | 1022 | United States | Mar 1921 | Sep 2013 |
| ONION MOUNTAIN LOOKOUT OREGON | 296 | United States | Feb 1985 | Oct 2013 |
| ONION PARK | 119 | United States | Mar 2002 | Oct 2013 |
| ONLEY 1 S | 423 | United States | Sep 1918 | Nov 1955 |
| ONO-I-LAU MANUAL | 797 | Fiji | Jan 1943 | Oct 2013 |
| ONOR FORMER | 37 | Russia | Apr 1948 | Jan 1953 |
| ONSLOW AIRPORT | 549 | Australia | Jul 1943 | Oct 2013 |
| ONSLOW AUSTRALIA W. | 1483 | Australia | Jan 1887 | Jun 2012 |
| ONSLOW BAY | 34 | United States | Aug 2009 | Oct 2013 |
| ONSLOW BAY INNER | 58 | United States | Nov 2005 | Jun 2011 |
| ONSLOWAMO | 376 | Australia | Aug 1940 | Feb 1975 |
| ONTARIA MUNI | 192 | United States | Jun 1997 | Oct 2013 |
| ONTARIO INTERNATIONAL AP | 185 | United States | Jun 1998 | Oct 2013 |
| ONTARIO INTERNATIONAL ARPT | 594 | United States | Jan 1897 | Dec 2004 |
| ONTARIO MUNICIPAL AP | 804 | United States | Jul 1945 | Oct 2013 |
| ONTONAGON | 52 | United States | Feb 2007 | Jun 2011 |
| ONTONAGON 6 SE | 944 | United States | Apr 1900 | Oct 2013 |
| ONTONAGON 8WSW | 20 | United States | Jan 2011 | Sep 2012 |
| ONWARD | 438 | United States | Dec 1954 | Feb 1992 |
| ONYANG | 252 | Korea, South | Jan 1973 | Dec 1993 |
| OODNADATTA AIRPORT | 796 | Australia | Apr 1939 | Oct 2013 |
| OODNADATTA POLICE STATION | 39 | Australia | Sep 1985 | May 1991 |
| OOKALA 223 | 862 | United States | Jan 1919 | Sep 1993 |
| OOLITIC PURDUE EXP FARM | 1256 | United States | Feb 1893 | Oct 2013 |
| OOLITIC-PURDUE-EXP-F | 971 | United States | Feb 1893 | Dec 1990 |
| OOLOGAH DAM | 383 | United States | Sep 1956 | Oct 2013 |
| OONIKUP,MA | 154 | Canada | Apr 1890 | May 1903 |
| OOST MAARLAND AWS | 23 | Netherlands | Nov 1994 | Mar 1999 |
| OOSTENDE (AIRPORT) | 504 | Belgium and Luxemborg | Jul 1940 | Oct 2013 |
| OOSTENDE (PIER) | 360 | Belgium and Luxemborg | Jan 1973 | Dec 2005 |
| OOTMOED | 8 | Namibia | Jul 2009 | May 2010 |
| OOTSA L SKINS L SPILLWAY,BC | 641 | Canada | Dec 1956 | Jan 2013 |
| OOTSA LAKESKINS LAKE CLIMATE, BC | 94 | Canada | Nov 2005 | Oct 2013 |
| OPAEULA 870 | 905 | United States | Jan 1919 | Feb 2013 |
| OPAL | 12 | United States | Apr 1916 | Dec 1920 |
| OPAL MOUNTAIN CALIFORNIA | 249 | United States | Oct 1991 | Oct 2013 |
| OPARINO | 707 | Russia | Jan 1950 | Oct 2013 |
| OPELIKA | 632 | United States | Apr 1957 | Oct 2013 |
| OPELOUSAS AIRPORT | 279 | United States | Feb 1893 | Jul 1918 |
| OPEN POND - FTS ALABAMA | 155 | United States | Jul 1998 | Oct 2013 |
| OPHEIM | 172 | United States | Dec 1928 | Jul 1943 |
| OPHEIM 10 N | 612 | United States | May 1959 | Oct 2013 |
| OPHEIM 12 SSE | 834 | United States | Aug 1943 | Aug 2013 |
| OPHIR | 30 | United States | Jul 1938 | Mar 1942 |
| OPIDS CAMP FC 57 B E | 251 | United States | Jan 1933 | May 1958 |
| OPIHIHALE NO 2 24.1 | 670 | United States | Jul 1956 | Sep 2013 |
| OPOCHKA | 13 | Russia | Sep 2012 | Oct 2013 |
| OPOLE | 753 | Poland | Jan 1951 | Oct 2013 |
| OPORNY | 23 | Kazakhstan | Oct 1987 | Jun 1990 |
| OPPAMA | 106 | Japan | Jul 1951 | May 1960 |
| OPPDAL-SETER | 160 | Norway | Apr 2000 | Oct 2013 |
| OPPIN | 53 | Germany | Sep 1938 | Dec 1943 |
| OPTIMA LAKE | 104 | United States | Dec 1985 | Oct 1994 |
| OQUOSSOC (1) | 127 | United States | Jan 1904 | May 1969 |
| OR TAMBO INTL ARPT | 450 | South Africa | Dec 1975 | Oct 2013 |
| ORACLE STATE PARK | 1286 | United States | Jan 1893 | Sep 2013 |
| ORACOKE (CGS) | 85 | United States | Oct 1975 | Apr 1986 |
| ORADEA RUMANIA | 727 | Romania | Jan 1951 | Oct 2013 |