The largest man-made crater in the United States is twelve miles southwest of what lake?
Sedan (nuclear test):  The Sedan Crater is the largest man-made crater in the United States, and is listed on the National Register of Historic Places. Sedan Crater: Sedan Crater is the result of the Sedan nuclear test and is located within the Nevada Test Site, 12 mi southwest of Groom Lake, Nevada (Area 51).
Groom Lake