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?
Context: The American River Parkway is a 23 mi parkway that runs along the American River throughout Sacramento County, California and consists of many smaller parks and boat launching points.  It can be accessed by various exits off U.S. Route 50 in Sacramento County. The Capital SouthEast Connector is a 34 mi planned parkway in California running from Interstate 5 (I-5) to U.S. Route 50 (US 50).  The route runs through Sacramento County, Elk Grove, Rancho Cordova, Folsom, and El Dorado County.  This project serves as an alternative route to the Greater Sacramento region's current highway system.  It consists of four to six lanes of thoroughfare and expressway; the connector phase I is projected to be completed around 2022–25, phase II around 2030–40. Tyndall Air Force Base is a United States Air Force Base located 12 mi east of Panama City, Florida.  The base was named in honor of World War I pilot 1st Lt Frank Benjamin Tyndall.  The base operating unit and host wing is the 325th Fighter Wing (325 FW) of the Air Combat Command (ACC).  The base is delineated as a census-designated place and had a resident population of 2,994 at the 2010 census. Mather is a census-designated place in Sacramento County, California.  Mather sits at an elevation of 108 ft .  The 2010 United States census reported Mather's population was 4,451.  It is the site of the former Mather Air Force Base, closed by the federal government in 1993. Sacramento Mather Airport (IATA: MHR, ICAO: KMHR, FAA LID: MHR) , also known as simply Mather Airport, is a county-owned public-use airport located 10 nautical miles (19 km) east of the central business district of Sacramento, in Sacramento County, California, United States.  It is located on the site of the former Mather Air Force Base which was closed in 1993. East Sacramento (also known as East Sac) is a neighborhood in Sacramento, California, United States, that is east of downtown and midtown.  East Sacramento is bounded by U.S. Route 50 to the south, Alhambra Boulevard to the west, Elvas Avenue to the north and northeast, and California State University, Sacramento and the American River to the southeast.  East Sacramento residential development began in the 1890s, and the area was annexed into Sacramento in 1911.  East Sacramento was also home to the Alhambra Theatre.  East Sacramento also includes McKinley Park and the "Fabulous Forties" neighborhood. The Tower Bridge is a Vertical lift bridge across the Sacramento River, linking West Sacramento in Yolo County to the west, with the capital of California, Sacramento, in Sacramento County to the east.  It was previously a part of U.S. Route 40 until that highway was truncated to east of Salt Lake City.  The bridge is maintained by the California Department of Transportation as part of State Route 275 and connects West Capitol Avenue and Tower Bridge Gateway in West Sacramento with the Capitol Mall in Sacramento. Mather Air Force Base (Mather AFB) was a United States Air Force Base, which was closed in 1993.  It was located 12 mi east of Sacramento, on the south side of U.S. Route 50 in Sacramento County, California.  Mather Field was one of 32 Air Service training camps established after the United States entry into World War I in April 1917. Mather Field/Mills is a side platformed Sacramento RT light rail station in Rancho Cordova, California, United States.  The station was opened on September 6, 1998, and is operated by the Sacramento Regional Transit District.  As part of the Gold Line, it has service to Downtown Sacramento, California State University, Sacramento, Gold River and Folsom.  The station is located near the intersection of Mather Field Road and Folsom Boulevard, is served by various RT bus routes and serves the nearby Mather Air Force Base. McClellan Air Force Base (1935–2001) is a former United States Air Force base located in the North Highlands area of Sacramento County, 7 mi northeast of Sacramento, California.
Answer: 1993