Cannikin Nuclear Test Site, Alaska
The largest underground nuclear test conducted by the United States, Project Cannikin was one of three underground nuclear tests performed at different places on this 42-mile long island in the Aleutian Chain. This $200 million 1971 test was performed to test an Anti-Ballistic Missile warhead, for a Spartan ABM missile. It consisted of a 5 megaton-yield thermonuclear bomb, detonated in a 50-foot diameter chamber, at the bottom of a 5,875-foot shaft. The resulting explosion was said to have had the force of a 7.0 magnitude earthquake, as measured on the Richter scale. The island of Amchitka was a military outpost in WWII, and the air field and base camp from that facility were reused for the nuclear testing program.