Both the Atlas and Titan I IBCMs used non-storable propellants (primarily kerosene/LOX). They had to be erected and fueled before they could be launched. That took too long, so the storable propellant Titan II and the solid fueled Minuteman ICBMs were quickly developed. If memory serves, the first Minuteman unit was activated shortly before the Cuban Missile Crisis and the Atlas ICBMs were deactivated a year or two later.
Atlas ICBMs were converted to space launchers and served in that capacity for decades. To the best of my knowledge, they never did that with the Titan Is but I can't find a reason why. Perhaps they were used for other things (e.g. ABM target vehicles) or perhaps they were just scrapped. I've seen a couple Titan Is in museums but don't know a lot about the missile's history other than it was developed at the same time as the Atlas as a contingency (just as the B-32 Dominator was a contingency for the B-29 Superfortress).
Space/Science » in reply to Missiles
The Atlas and Titan I ICBMs were only operational for a few years