Map (plastic coated) - Fort Lewis, Washington Special. Fort Lewis is a United States military facility located 14.6 km south-southwest of Tacoma, Washington under the jurisdiction of the United States Army Joint Base Garrison, Joint Base Lewis–McChord. Fort Lewis, named after Meriwether Lewis of the famed Lewis and Clark expedition, is one of the largest and most modern military reservations in the United States. Consisting of 87,000 acres of prairie land cut from the glacier-flattened Nisqually Plain, it is the premier military installation in the Northwest. Fort Lewis was originally established in 1917 with the passage of a Pierce County bond measure to purchase 70,000 acres of land to donate to the federal government for permanent use as a military installation.