Maryland Route 45

Maryland Route 45 (MD 45) is a state highway in the U.S. state of Maryland. Known for most of its length as York Road, the state highway runs 30.06 miles (48.38 km) from U.S. Route 1 (US 1) in Baltimore north to the Pennsylvania state line in Maryland Line, where the highway continues as SR 3001. MD 45 is the primary highway between Downtown Baltimore and Towson, the county seat of Baltimore County. North of Interstate 695, the state highway parallels I-83 and serves the suburban communities of Lutherville, Timonium, Cockeysville, and Hunt Valley. MD 45 also connects the northern Baltimore County communities of Hereford and Parkton. The state highway is maintained by the Maryland State Highway Administration in Baltimore County and by the Baltimore City Department of Transportation in the city, where the highway also follows Greenmount Avenue.

York Road, which follows the path of an 18th century wagon road and 19th century turnpike, was one of the original state roads marked for improvement by the Maryland State Roads Commission in 1909. The state highway was constructed as an all-weather road in the mid-1910s from Baltimore to Hereford. The remainder of York Road to Maryland Line was built in the late 1910s and early 1920s. York Road was designated US 111 in 1927 and widened to handle the increasing traffic load in the late 1920s. York Road became a secondary route when a freeway was constructed from Baltimore to York and Harrisburg in the 1950s. US 111 was moved to this freeway as sections opened; the old road became MD 45. MD 45 fully replaced US 111 on York Road when the U.S. Highway was replaced by I-83 in the early 1960s.