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?

full_context: Document 1: McClellan 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.
Document 2: Fresno Air Attack Base: The Fresno Air Attack Base was established in 1955 By the US Forest Service, Sierra National Forest and is located at the Fresno Yosemite International Airport. The US Forest Service leases office space to the California Department of Forestry and Fire Protection's (CAL FIRE) Fresno/Kings Unit. In 1994, it was completely rebuilt to become a model modern AirTanker Base which includes a modern interagency communication/command center.
Document 3: Sacramento International Airport: Sacramento International Airport (IATA: SMF, ICAO: KSMF, FAA LID: SMF) is 10 mi northwest of downtown Sacramento, in Sacramento County, California. It is run by the Sacramento County Airport System. Southwest Airlines carries about half the airline passengers.
Document 4: SMF Automated People Mover: The SMF Automated People Mover is an elevated automated people mover system at Sacramento International Airport in Sacramento, California. The system opened on October 6, 2011, and is used to move passengers between Central Terminal B (landside) and Concourse B (airside). The system uses two Bombardier Innovia APM 100 vehicles operating as single cars on two separate parallel tracks.
Document 5: McClellan AFB Annex: McClellan Air Force Base Annex #1 ("McClellan Anx #1") was a military installation near McClellan Air Force Base in Contra Costa County, California, that was active from 28 November 1951 to 2 July 1956. Strategic Air Command operated an (call sign "Sacramento Bomb Plot") just outside the base at Whitney and Eastern Avenues.
Document 6: Aerospace Museum of California: The Aerospace Museum of California is an aviation museum located in North Highlands, California on the grounds of the former McClellan Air Force Base. It features displays of authentic military and civilian aircraft as well as space vehicle replicas. It preserves the history and mission of this former base as well as those of neighboring bases like Beale (active) and Mather (closed) Air Force Bases. McClellan Air Force Base closed in 2001 and became McClellan Airfield, a civil aviation airport.
Document 7: Mammoth Yosemite Airport: Mammoth Yosemite Airport (IATA: MMH, ICAO: KMMH, FAA LID: MMH) is a town-owned public airport seven miles east of Mammoth Lakes, in Mono County, California. Also known as Mammoth Lakes Airport or Mammoth-June Lake Airport, it is mainly used for general aviation, but has scheduled passenger flights operated by two airlines, one of which only serves the airport on a seasonal basis during the winter sports season.
Document 8: Bakalar Air Force Base: Bakalar Air Force Base is a former U.S. Air Force base located 4.4 mi northeast of Columbus, Indiana. During World War II, the base was known as Atterbury Air Field and Atterbury Army Air Base (named in memory of Brigadier General William Wallace Atterbury), but it was renamed Bakalar Air Force Base in 1954 in honor of First Lieutenant John Edmond Bakalar, USAAF. Established in 1942, the airfield served as a training base for medium-range C-46 Commando and C-47 Skytrain troop carrier planes and glider pilots. It also was used for training B-25 Mitchell and B-26 Marauder bomber crews. Reactivated during the Cold War, it was used as an Air Force Reserve training base for troop carrier, tactical airlift, and special operations flying units. The military base was closed in 1970. The present-day facility operates as the Columbus, Indiana, municipal airport.
Document 9: Mather Air Force Base: 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.
Document 10: Sacramento Mather Airport: 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.
Document 11: Mather Field / Mills (Sacramento RT): 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.
Document 12: March Air Reserve Base: March Air Reserve Base (IATA: RIV, ICAO: KRIV, FAA LID: RIV) (March ARB), previously known as March Air Force Base (March AFB) is located in Riverside County, California between the cities of Riverside and Moreno Valley. It is the home to the Air Force Reserve Command's 4th Air Force (4 AF) Headquarters and the host 452d Air Mobility Wing (452 AMW), the largest air mobility wing of the 4th Air Force. In addition to multiple units of the Air Force Reserve Command supporting Air Mobility Command, Air Combat Command and Pacific Air Forces, March ARB is also home to units from the Army Reserve, Navy Reserve, Marine Corps Reserve, California Air National Guard and the California Army National Guard. For almost 50 years, March AFB was a Strategic Air Command base during the Cold War.
Document 13: K. I. Sawyer Air Force Base: K. I. Sawyer Air Force Base is a decommissioned U.S. Air Force installation in Marquette County, Michigan, south of the city of Marquette. Near the center of Michigan's Upper Peninsula, the base operated for nearly forty years and closed in 1995. The county airport, Sawyer International, now occupies a portion of the base and has scheduled airline flights and some general aviation activity. The area of the former base is now an unincorporated community and a census-designated place for statistical purposes known as K. I. Sawyer AFB
Document 14: Mather, Sacramento County, California: 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.
Document 15: McClellan Park, California: McClellan Park is a census-designated place in Sacramento County, California. McClellan Park sits at an elevation of 69 ft . The 2010 United States census reported McClellan Park's population was 743. It is the site of the former McClellan Air Force Base, closed by the federal government in 2003.
ground_truth: 1993