Maryland Route 24 consists of three distinct segments: a mostly-divided highway from the Edgewood Arsenal, through Edgewood, Abingdon and Bel Air; a concurrency with U.S. Route 1 along the Bel Air Bypass; and a two-way trafficway through Forest Hill, Rocks State Park and to the Pennsylvania line. The first of these segments directly replaced what is now Maryland Route 924 through the area.