On This Day in History / April 20, 2023 1962: The first Titan I ICBM begins operational alert at Lowry AFB, Colorado. The Martin Marietta SM-68A/HGM-25A Titan I was the United States’ first multistage intercontinental ballistic missile (ICBM), used from 1959 to 1962. Though the SM-68A laid the groundwork for numerous follow-on models that were a part of the U.S. arsenal and space launch capability. (Stock Image)