MD 7 is the old alignment of US 40 in northeastern Maryland. The route was first laid out early in colonial times and later formed part of the post road between Baltimore and Philadelphia (going further north to New York City and into New England to Boston) and between the northern and southern of the original Thirteen Colonies on the East Coast. The highway in Baltimore and Harford counties became a turnpike, constructed and operated by a private stockholder company in the early 19th century. The Maryland State Roads Commission (established 1908 - now the Maryland State Highway Administration within the Maryland Department of Transportation since the early 1970s) marked portions of what became known as the Philadelphia Road, close to Baltimore and between Perryville and Elkton for improvement as state roads in 1909. Those sections and the highway between Aberdeen and Havre de Grace were constructed as modern roads in the early to mid-1910s. The remainder of the highway was constructed in the 1920s and designated as US 40 in 1927. The high volume of traffic and the required continuous expansion of the highway led the old Maryland State Roads Commission to construct the modern Pulaski Highway (mamed for the foreign military volunteer of a Polish cavalry officer Casimir Pulaski (1745-1779), who fought in the American Revolutionary War (1775-1783), which was constructed during the "Great Depression" years between 1935 and 1941. Old sections of US 40 became segments of MD 7 between 1938 and 1941 as portions of the new four-lane divided highway were opened from Baltimore to Elkton.