Known for much of their length as Philadelphia Road, there are five disjoint mainline sections of the highway totaling 40.23 miles (64.74 km) that parallel U.S. Route 40 (US 40) in Baltimore, Harford, and Cecil counties in northeastern Maryland.

The next segment of the state highway is a C-shaped route through Havre de Grace on the west bank of the Susquehanna River.

The highway in Baltimore and Harford counties became a turnpike, constructed and operated by a private stockholder company in the early 19th century.

Those sections and the highway between Aberdeen and Havre de Grace were constructed as modern roads in the early to mid-1910s.

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 (named for the 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.

MD 7 heads northeast as a two-lane undivided street through a residential neighborhood with scattered businesses and industrial properties as well as a crossing of Redhouse Creek.

[1][2] MD 7 expands to a five-lane highway with a center left-turn lane as it approaches Campbell Boulevard in White Marsh.

The road passes through forest with isolated residential subdivisions, with roundabouts located at Seven Trails Drive and Holly Oak Circle.

The route comes to a grade crossing with Norfolk Southern Railway's Havre de Grace Industrial Track.

The state highway turns north onto Union Street, which heads south as MD 490, adjacent to University of Maryland Harford Memorial Hospital.

Immediately after passing under the Amtrak Susquehanna River Bridge, MD 7 turns west onto Otsego Street.

The road crosses Juniata Street, where a park and ride lot is located on the southwest corner of the intersection.

[1][3] MD 7 begins at the entrance to the Perry Point VA Medical Center just north and east of the Amtrak Susquehanna River Bridge adjacent to Rodgers Tavern in the town of Perryville.

The highway heads east as two-lane undivided and municipally maintained Broad Street, passing under both railroad tracks of the wye of Norfolk Southern Railway's Port Road Branch line with Amtrak's Northeast Corridor, within which is the Perryville station that serves as the terminus of MARC's Penn Line.

The highway heads southeast as two-lane undivided Old Philadelphia Road in a forested area between a pair of quarries.

The highway intersects MD 272, which follows a one-way pair, Main Street southbound and Mauldin Avenue northbound.

MD 7 continues east, passing Old Elk Neck Road before turning north and reaching its eastern terminus at US 40.

[1][6] The rough alignment of what is now MD 7 in Baltimore and Harford counties existed by 1695 as a rudimentary road; Baltimore County ordered that the road be widened to 30 feet (9.1 m) in width to allow easy passage for carts and for bridges to replace ferries at the numerous creeks along the route.

The highway was paved as an 18-foot (5.5 m) wide tarred macadam road from Elwood Avenue to Herring Run in 1910.

[14] The highway was paved in concrete along Main Street and Delaware Avenue through Elkton, with the exception of a gap at the west end of town, by 1923.

The 1,100-foot (340 m) gap at the west end of Elkton was left in inferior condition in anticipation of a grade separation of the Pennsylvania Railroad.

The state highway was widened with dual 7 feet (2.1 m) shoulders from the Baltimore city limit to Rossville in 1938.