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Unknown, Atlas missile launch from Vandenberg Air Force Base, 18 February 1981, National Archives and Records Administration, Records of the Office of the Secretary of Defense

Issue Brief

Atlas E Missile Program

The northern plains of Colorado—Larimer and Weld counties—served as the home of five Atlas E missile sites equipped with plutonium-based nuclear warheads. Colorado and the Denver area were chosen for Atlas missiles because of the proximity to other important military infrastructure. The host military base for the Atlas E program’s command and control was located in Francis E. Warren Air Force Base in Cheyenne, Wyoming.

One of the U.S.’s first operational intercontinental ballistic missiles, the 82-foot-long Atlas E missile was fueled by kerosene and liquid oxygen and was designed to carry a nuclear warhead. Developed in the late 1950s, the first Atlas E missiles became operational in late 1961. The Atlas E model developed within a heated technical debate about the utility of investing in rocket-powered ballistic missiles versus air-breathing cruise missiles. Within the tense context of the Cold War, the Air Force concluded that if the U.S. were to achieve an intercontinental ballistic missile capability first, it could maintain an advantage over the USSR, and so it decided to cut the cord on its two primary air-breathing cruise missiles, the SM-64 Navaho and SM-62 Snark programs, and recategorize the SM-65 Atlas to 1-A top priority status.   

Two years later, in 1957, the Air Force produced and launched its first SM-65 Atlas missile and subsequently continued with a series of non-operational, prototype models labeled Atlas A, B, and C. On October 31, 1959, the deployment of Atlas D to Vandenberg Air Force Base in San Diego marked the SM-65’s first deployment. Over the following six years the upgraded Atlas E and F were deployed across the United States. During the Cuban missile crisis in October 1962, the Atlas Es were readied for launch as a “deterrent.” The Atlas F model was 27 feet high and 40 feet wide, and featured an all-inertial guidance system and an engine with 390,000 pounds of thrust. At the program’s peak, 132 Atlas sites were operational from December 1962 through May 1964. The missiles had a short operational life, however, and were phased out in 1965 in favor of the Minuteman and Titan ICBMs.

Atlas sites in Colorado were decommissioned and the missiles removed in 1965. The complexes were then sold to public and private owners: two were used for commercial purposes, one was converted into a residence, one was covered with soil, and one became the Weld County Missile Park. Most of the decommissioned silos have been destroyed or abandoned, but the Missile Site Park—located between Greeley, Windsor, and Loveland—offers free tours of the former launch facility and camping near the silo’s concrete pad for $5/night.

After the decommissioning and removal of missiles from northern Colorado, the U.S. Army Corps of Engineers conducted multiple investigations into the program’s environmental and social impacts in the area. Groundwater contamination by trichloroethylene (TCE) remains the greatest concern at the Atlas sites. This cleaning solvent was used by missile crews to flush out the fuel tanks after missile readiness tests; the crews dispersed spent TCE and other residual chemicals in a sump below the launch buildings, which then entered shallow groundwater.


Colorado Department of Public Health and Environment. "Atlas Missile Sites." 2019. Accessed August 3, 2020.

Colorado Department of Public Health and Environment, U.S. Environmental Protection Agency, and U.S. Army Corps of Engineers. "Fact Sheet: Atlas Missile Sites in Colorado." Fall 2003. Accessed August 3, 2020.

Federation of American Scientists. "SM-64 Navaho." FAS.org. July 17, 1998 [last updated]. Accessed August 3, 2020.

U.S. Department of State, Office of the Historian. "Report by the Technological Capabilities Panel of the Science Advisory Committee." Foreign Relations of the United States, 1955-1957. National Security Policy XIX, Document 9. February 14, 1955. Accessed August 3, 2020.

Weld County Colorado. "Missile Site Park." Accessed May 10, 2021.

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