The Mesa Laboratory of the National Center for Atmospheric Research (NCAR) stands on a site of more than 400 acres (160 hectares) at the southwestern edge of Boulder, Colorado. This site was presented to the National Science Foundation, NCAR's sponsor, by the state of Colorado. An additional 120 acres west of this site were deeded to the City of Boulder by the U.S. government as an addition to Boulder's mountain parks. NCAR is a major access point for trails in this parks system. Several mountain trails branch off from the handicap-accessible Walter Orr Roberts Weather Trail. Located immediately behind the Mesa Lab, it is the only interpretive weather trail in the United States.