Atlas D - range 10,360 miles
The Atlas D was initially a prototype of the operational Atlas ICBM. Designed for testing of all Atlas operating systems, it became the first operational US ICBM. SAC was so optimistic about the missile that it began constructing operational launch sites before the Atlas D test flights had even begun. This was largely motivated by a perceived "missile gap" existed between the U.S. and the Soviet Union.
The Atlas D was nearly identical to the Atlas C, although the two booster engines were upgraded to provide a combined thrust of 367,000 pounds at liftoff, compared to 330,000 pounds for the Atlas C. The thrust of the sustainer engine and vernier engines remained the same. Test-flight profiles for the Atlas D were designed specifically to simulate operational conditions of a deployed and activated ICBM.
Optimism soon turned to dismay. The first Atlas D was launched from Cape Canaveral on April 14, 1959, followed by ones May 18th and June 6th. All three missiles exploded less than three minutes into their flights.
The fourth Atlas D launched from the Cape completed a successful test flight on July 28, 1959. One out of four wasn't bad, so the Atlas D was declared operational a little over two months later. They were deployed at Vandenberg Air Force Base, California, Offutt Air Force Base, Nebraska and Warren Air Force Base, Wyoming. These first operational Atlas D missiles were intended to be launched from a vertical storage position on surface-level gantry-serviced launch pads. But to increase safety and security, facilities were modified to allow the Atlas D to be stored horizontally in a concrete surface bunker. The missile could be raised then fueled for a quick launch, which could typically be accomplished in as little as 15 minutes.