In Maryland, Interstate 70 runs horizontally from the Pennsylvania state line near Hancock east across the central portion of the state towards Baltimore, following the route of the National Road, now known as U.S. 40. It is the major east-west highway in the state, serving the cities of Hagerstown and Frederick and bypassing Ellicott City; east of Frederick, the route was originally designated Interstate 70N. The route serves Washington D.C. via Interstate 270, which was once designated Interstate 70S. Uniquely, Interstate 70 indirectly serves a branch of the Washington Metro at Shady Grove via Interstate 370, which only connects to Interstate 270.
I-70 was planned to end at Interstate 95 in Baltimore, but due to local opposition, it was only built to Maryland Route 122 (see History below). The pavement that was supposed to be part of the route to Baltimore is now a Park and ride.