- Southern Terminus:
- North of Fork Road and Long Green Pike in Baldwin
- Northern Terminus:
- Delta Road (PA 74) at the Maryland-Pennsylvania state line
- 20.38 miles
- Baltimore, Harford
MD 165 is an extension of PA 74 south into Maryland. Baldwin Mill Road begins at Fork Road and Long Green Pike in Baldwin. At first, it is a local road, but it takes on the MD 165 designation after a short distance. MD 23 multiplexes with MD 165 along Baldwin Mill Road for about a mile in Jarrettsville. After the two routes split, MD 165 changes names to become Federal Hill Road. After another few miles, there is a traffic circle at Rocks Road (MD 24). There, MD 165 changes names again to become Pylesville Road. It continues north to the border with Pennsylvania, where it becomes Delta Road (PA 74). The entire length is a two-lane undivided road through rural surroundings.