The Titan program began development in 1955 as a back up option in case the Atlas program failed. It would become the second Intercontinental Ballistic Missile (ICBM) deployed by the U.S. Air Force. Also a liquid fueled giant, the Titan was the first multi-stage ICBM put on operational alert.
Based within super-hardened silos, deep beneath the ground, the Titan's concrete and steel reinforced facilities were able to withstand the massive pressure of a nuclear blast. This gave it a survivability from nuclear attack, that the Atlas lacked.
The first successful test of a Titan took place in January of 1960. A little over two years later, the first Titan I's became operational, based out of Lowry Air Force Base in Denver, Colorado in April 1962.