MD 165 passes through western and northern Harford County, where it connects the communities of Fallston, Jarrettsville, Pylesville, and Whiteford.

The state highway was constructed as part of MD 24 through Pylesville and Whiteford in the late 1910s and early 1920s.

Baldwin Mill Road continues south as part of a series of county roads—Fork Road, Sunshine Avenue, and Bradshaw Road—that parallel Little Gunpowder Falls along the eastern edge of Baltimore County through the communities of Baldwin, Fork, Kingsville, and Bradshaw.

[1][2] MD 165 continues north from Jarrettsville as Federal Hill Road, which passes through the namesake hamlet then curves east and crosses Deer Creek.

The state highway crosses Broad Creek and parallels Old Pylesville Road northeast through the village of Whiteford.

MD 165 was constructed north from Jarrettsville starting in 1924; the concrete highway reached Federal Hill in 1927.

MD 165 was completed when the final section of the modern highway was finished from west of Deer Creek to Bush's Corner in 1933.