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 "East Sacramento, Sacramento, California"): East Sacramento (also known as East Sac) is a neighborhood in Sacramento, California, United States, that is east of downtown and midtown.
Relevant evidence: No