[2] The stream flows southward for 21.5 miles (34.6 km) to its confluence with the Northeast Branch near Bladensburg to form the main stem of the Anacostia.

[3] The watershed in Montgomery County includes portions of the communities of Norwood, Bel Pre Manor, Colesville, Layhill, Glenmont, Wheaton, Hillandale, White Oak, Silver Spring, Kemp Mill, Four Corners, Woodmoor and Takoma Park.

Located at the north end of the Northwest Branch Trail, near the home of noted environmental author Rachel Carson, it is deliberately left rustic and unimproved.

[6] The majority of the Northwest Branch stream valley is a riparian buffer, protected as parkland by the Maryland-National Capital Park and Planning Commission (M-NCPPC).

Northwest Branch crosses the geological fall line between the Piedmont and Atlantic coastal plain regions, which forms a small waterfall on the stream 0.5 miles (0.80 km) south of the Burnt Mills Dam parks.