The following is the Nov. 23, 2022, Congressional Research Service report, Defense Primer: Ballistic Missile Defense.
From the report
The United States has been developing and deploying ballistic missile defenses (BMD) to defend against enemy missiles continuously since the late 1940s. In the late 1960s and early 1970s, the United States deployed a limited nuclear-tipped BMD system to protect a portion of its U.S. land-based nuclear ICBM (intercontinental ballistic missile) force in order to...
https://news.usni.org/2022/11/24/defense-primer-ballistic-missile-defense