June 11th, 1957. Developed as an ICBM and the first Intercontinental Ballistic Missile launched by the U.S., powered by kerosene and LOX. This is the Atlas rocket.
The Atlas A rocket was successfully launched in December of 1957 after two previous failed attempts, only powered by 2 engines. After this, Atlas B was launched with a sustainer engine in July of 1958, and the deployment of this rocket in December of the same year would be used to deliver a communication retransmitting satellite that President Eisenhower used to project a message to the people on Christmas.
Before Atlas D and Atlas Agena was the SM-65 Atlas rocket that served as a single-staged satellite carrier. However, this rocket was unstable under intense pressure and the necessity for nitrogen gas to keep it from collapsing became a burden.
One iteration that was used and highly reliable was Atlas Agena, which used a liquid-fueled genus stage on top of the rocket. The Agena stage of the Atlas rocket is one of the most commonly used rocket upper stages on U.S. rockets and helped launch payloads for the Mariner program. The final launch of Atlas Agena was observed in 1978.
Before both the Atlas Able and Atlas Agena was the Atlas D, which served as the main launch vehicle for the Mercury program. Atlas D was first utilized in 1959 to test the heat shields on the Mercury capsule; the launch came with many problems, such as defective engines and the capsule refusing to separate from the rocket, yet the heat shield worked at the end which labeled the mission a success.
Even after the Space Shuttle started, Atlas continued to develop its rockets for satellite launches, starting with the Atlas D Centaur which was created in 1962. After a failed launch, this rocket was reattempted in 1963, successfully resulting in the first liquid hydrogen engine in space. The design of Atlas-Centaur was simple, including both a liquid hydrogen and liquid oxygen (LOX) tank, as well as a spot for the payload, which was then covered by a nose fairing. Lastly, the payload capsule was powered by dual cryogenic RL-10 engines, which are still being used today for the ICPS on the SLS rocket.
After being decommissioned as an ICBM, the Atlas E and F rockets were developed and continued to send satellites to space until 1995. Atlas G and Atlas H were then produced with Atlas H being a rendition of the Atlas SM-65B while Atlas G was the same but had the Centaur upper stage equipped. After Atlas G/H came Atlas One, also known as Atlas I.
The roman numerals created a tricky naming scheme for the rocket, so Atlas I thus became Atlas One. This rocket used three RS-27 engines and was launched in 1990, also marking the end of the use of the Vernier engines. Atlas II came next in 1991 and served until 2004, using RS-56 engines instead. Atlas IIAS became a variation of the Atlas II which had four Castor side-rocket boosters attached to the outside of the rocket for increased thrust (like the Delta rockets). Atlas III had two variations: Atlas IIIA and Atlas IIIB. The Atlas IIIA used the RD-180 Russian engines to replace the RS-56 engines while the Atlas IIIB used a longer Centaur upper stage and two RL-10 engines instead of one. Atlas V is the last rocket that has been used, which uses five AJ-60 rocket motors instead of the Castor boosters.