Fort Lancaster, one in a series of forts erected along the western Texas frontier, is located in the Pecos River Valley in Crockett County, Texas, United States. The fort was established by Captain Stephen Decatur Carpenter on August 20, 1855, to guard the military supplies, commercial shipments, and immigrants moving along the San Antonio-El Paso Road. The 82 acre site, now operated by the Texas Historical Commission as Fort Lancaster State Historic Site, contains the ruins of twenty-nine buildings that made up the fort and a visitor center with a museum about the heritage of the fort.