Question: Sacramento Mather Airport is located on the site of a former air force base, located 12 mi east of Sacramento, on the south side of U.S. Route 50 in Sacramento County, California, which was closed in what year?
Sentence (from "Mather Air Force Base"): Mather Air Force Base (Mather AFB) was a United States Air Force Base, which was closed in 1993.
Relevant evidence: Yes