Key Dates
WSR-57: First operational unit commissioned June 26, 1959 in Miami, FL. Last unit decommissioned December 2, 1996 in Charleston, SC.
WSR-74: First WSR-74C installed August 1973 in Lubbock, TX. Last WSR-74C decommissioned end of 2012 in Williston, ND. Two variants: WSR-74S (S-band, network use) and WSR-74C (C-band, local use).
WSR-88D (NEXRAD): Operational prototype completed fall 1990 in Norman, OK. First operational unit June 12, 1992 in Sterling, VA. Initial deployment completed August 30, 1997. Network of 159 radars still in operation today.
AT&T Long Lines: Microwave relay network formally established in 1947. Coast-to-coast system opened August 17, 1951. Became AT&T Communications after 1984 Bell System breakup. Microwave towers largely decommissioned in early 1990s.
LORAN-A: First stations operational June 1942, system declared operational early 1943. Hyperbolic radio navigation system operating at 1.85-1.95 MHz. Phased out in North America December 31, 1980, rest of world by 1985.
LORAN-C: First operational chains deployed in 1957, operating at 90-110 kHz. Coast Guard took over operations in 1958. Opened to civilian use in 1974. US terminated operations February 8, 2010.
DEW Line: Distant Early Warning Line. Construction began December 1954, became operational July 31, 1957. Network of 63 radar stations across Arctic from Alaska to Greenland. Shut down in late 1980s, replaced by North Warning System starting in 1985.
Duga (prototype): Soviet over-the-horizon radar built near Mykolaiv, Ukraine. Started operating November 7, 1971. Experimental system for detecting missile launches.
Duga-1: Operational Soviet OTH radar near Chernobyl, Ukraine. Operated July 1976 to December 1989. Known as "Russian Woodpecker" for its distinctive 10 Hz signal that disrupted radio worldwide.
Duga-2: Operational Soviet OTH radar near Komsomolsk-on-Amur, Siberia. Operated July 1976 to December 1989.
North Warning System (NWS): Joint US-Canadian early warning radar system. Began limited operation in 1988, officially activated July 15, 1993, replacing the DEW Line. Consists of 47 radar sites across Canada's Arctic plus sites in Alaska. Still operational but considered obsolete against modern threats.
CONELRAD: Control of Electromagnetic Radiation. Established by President Truman in 1951, officially introduced December 10, 1951. First national emergency alert system using AM radio (640 and 1240 kHz). Replaced by EBS in 1963.
EBS: Emergency Broadcast System. Replaced CONELRAD in 1963. Used from 1963 to 1997. Featured the distinctive two-tone alert signal. Activated over 20,000 times for weather and local emergencies but never for a national emergency. Replaced by EAS on January 1, 1997.
EAS: Emergency Alert System. Became operational January 1, 1997, replacing EBS. Uses digital SAME (Specific Area Message Encoding) technology. Still in operation today for weather alerts, AMBER alerts, and other emergencies.