On this date in 1971, the U.S. tested the Cannikin device under Amchitka island. The purpose of the test was... well, as best as I can tell, to see how cool it would be to set off a really big nuke under an island in the Bering Sea. The test was eminently successful, releasing as much as five megatons of fun, and pissing off hippies to no end. (If you had a crew cut, a slide rule*, and a PhD, this is what you used to do instead of setting off M-80s under your neighbor's trash cans.)
Unfortunate side effects included guaranteed employment for government eco-types through at least 2025, and the formation of Greenpeace, but little of the kind of fallout that makes your kids have three heads.
*If you are even a tiny bit geeky, do not go read the Wikipedia entry on slide rules. You will fall down the rabbit hole and not come out for hours. You have been warned.