The state highway heads east as a two-lane undivided road through farmland that passes through a pair of curves in the hamlet of Oak Orchard before crossing Sams Creek into Carroll County at Englars Mill.

The state highway crosses the east–west line of the Maryland Midland Railway at-grade and heads north through the New Windsor Historic District as High Street.

MD 31 turns south onto Green Valley Road, then turns east onto Main Street one block east of its previous intersection with Main Street.

[1][2] Prior to leaving the town of New Windsor, MD 31 intersects Springdale Road, passes the historic Avalon, and meets the western end of its old alignment, which is named Old New Windsor Road and is unsigned MD 852.

The old alignment closely parallels the present alignment immediately to the south as the two roads approach the city limit of Westminster, where MD 31 veers north and MD 852K continues northeast to its terminus in the Western Maryland College Historic District.

MD 31 intersects Uniontown Road and Main Street / WMC Drive west of downtown Westminster and passes along the western edge of the McDaniel College campus before reaching its northern terminus at MD 140 (College View Boulevard).

[8] MD 31 from Westminster to New Windsor was started in 1919; the 15-foot (4.6 m) wide concrete road between the two towns was completed by 1921.

[10] By 1923, concrete roads were constructed from just east of Libertytown to north of Unionville and for 1 mile (1.6 km) south from New Windsor.

[13] The state highway was widened with a pair of 3-foot (0.91 m) macadam shoulders from Westminster to New Windsor between 1936 and 1939, resulting in a 21-foot (6.4 m) wide roadway between the two towns.

[14] A disjoint section of MD 31 was added in 1939 along Water Tank Road east of Manchester.