Maryland Route 4 | ||||
|---|---|---|---|---|
 Maryland Route 4 highlighted in red | ||||
| Route information | ||||
| Maintained by MDSHA | ||||
| Length | 64.85 mi[1] (104.37 km) | |||
| Existed | 1927–present | |||
| Tourist routes |  Star-Spangled Banner Scenic Byway | |||
| Major junctions | ||||
| South end |  MD 5 in Leonardtown | |||
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| North end | Pennsylvania Avenue at the District of Columbia boundary near Suitland | |||
| Location | ||||
| Country | United States | |||
| State | Maryland | |||
| Counties | St. Mary's, Calvert, Anne Arundel, Prince George's | |||
| Highway system | ||||
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Maryland Route 4 (MD 4) is a state highway in the U.S. state of Maryland. The highway runs 64.85 miles (104.37 km) from MD 5 in Leonardtown north to Southern Avenue in Suitland at the District of Columbia boundary, beyond which the highway continues into Washington as Pennsylvania Avenue. MD 4 is a four- to six-lane highway that connects Washington and communities around Interstate 95 (I-95)/I-495 (Capital Beltway) with southern Prince George's County with southwestern Anne Arundel County. The highway is the primary highway for the length of Calvert County, during most of which the route runs concurrently with MD 2. MD 4 also connects Calvert and St. Mary's counties via the Governor Thomas Johnson Bridge across the Patuxent River. The highway connects the Southern Maryland county seats of Leonardtown, Prince Frederick, and Upper Marlboro.
MD 4 is one of the original Maryland state highways. The state highway followed roughly its present alignment through Prince George's County, then headed east through Anne Arundel County along what is now MD 408. In the 1960s, MD 4 took over MD 416 (Southern Maryland Boulevard) southeast to Sunderland and joined MD 2 all the way to Solomons. After the Governor Thomas Johnson Bridge opened in the late 1970s, MD 4 was extended west from Solomons to Leonardtown. MD 4 has been upgraded to a divided highway for most of its length, beginning in the early 1960s from Washington, reaching Solomons in the mid-1980s, and expected to continue into St. Mary's County in the future.