Fort Lewis was a United States Army post from 1917 to 2010 located 9.1 miles (14.6 km) south-southwest of Tacoma, Washington. Fort Lewis was merged with McChord Air Force Base on 1 February 2010 to form Joint Base Lewis–McChord. Fort Lewis, named after Meriwether Lewis of the Lewis and Clark Expedition, was one of the largest and most modern military reservations in the United States. Consisting of 87,000 acres (350 km2) of prairie land cut from the glacier-flattened Nisqually Plain, it is the premier military installation in the northwest and is the most requested duty station in the army.