MD 231 begins at an intersection with Olivers Shop Road in the hamlet of Burnt Store in eastern Charles County. Olivers Shop Road connects Dentsville to the south with Bryantown to the north. MD 231 heads east as two-lane undivided Burnt Store Road, crossing Gilbert Creek on its way to Hughesville. Within Hughesville, the state highway intersects MD 5 Business (Old Leonardtown Road), where the highway's name changes to Prince Frederick Road. East of the village center, MD 231 meets MD 5 (Leonardtown Road) at a dumbbell interchange. In the hamlet of Patuxent, the state highway intersects the southern terminus of MD 381 (Brandywine Road), which heads north into the southeastern corner of Prince George's County.^[1][2]

From Patuxent, MD 231 heads southeast through the neck of far eastern Charles County that reaches to the Patuxent River between Prince George's County and St. Mary's County. Before reaching the river, the state highway passes to the north of the village of Benedict, which was the site of the landing of British troops to march toward Washington, D.C., prior to the Battle of Bladensburg during the War of 1812.^[1][2][3] The state highway crosses the Patuxent River on the Benedict Bridge, a 3,343-foot (1,019 m) long steel beam bridge whose roadway is 24 feet (7.3 m) wide.^[4] At the Patuxent River's navigation channel, the bridge features a through steel girder swing span that has 17 feet (5.2 m) vertical clearance when closed and provides two openings with 50 feet (15 m) horizontal clearance when opened.^[5]

MD 231 enters Calvert County at Hallowing Point and continues east as Hallowing Point Road, passing an industrial park and Hallowing Point Park. After intersecting the northern terminus of MD 508 (Adelina Road), the state highway veers northeast through the village of Barstow, where the highway passes west of a park and ride lot and the Calvert County Fairgrounds before it intersects Barstow Road, which serves the historic homes Cedar Hill and Willow Glenn. MD 231 passes the Prince Frederick campus of the College of Southern Maryland before entering Prince Frederick. The state highway meets MD 2/MD 4, which run concurrently as Solomons Island Road, on the west side of the county seat. MD 231 continues northeast as Church Street, passing the historic home Linden, home of the Calvert County Historical Society. The state highway reaches its eastern terminus at MD 765 (Main Street), a short distance north of the county courthouse.^[1][2]

MD 231 is a part of the main National Highway System from MD 5 in Hughesville to MD 2/MD 4 in Prince Frederick.^[1][6]

The Prince Frederick Road portion of MD 231, originally named Benedict Road, was constructed as a gravel road by 1921.^[7] The Hallowing Point Road section was built in gravel around 1923.^[8] Burnt Store Road was constructed of gravel starting in 1930 and was completed by 1933.^[9][10] At MD 231's western terminus, Olivers Shop Road was originally MD 232, which ran from MD 234 at Wicomico north to what was then MD 233 (Woodville Road) north of Bryantown.^[11] MD 232 was removed from the state highway system around 1989, leaving MD 231's western terminus at a county highway.^[12]

Ferry service began between Benedict and Hallowing Point began around 1933.^[10] On the west side of the Patuxent River, MD 231 originally turned south into the village of Benedict, following Benedict Avenue to the ferry terminal where the avenue starting following the riverbank. The Hallowing Point terminal remains today as a boat ramp immediately south of the bridge.^[13] State senator Louis L. Goldstein of Calvert County sponsored a bill to construct a bridge between Benedict and Hallowing Point. In order to get enough votes to pass, the bridge bill stipulated the bridge would have a 25-cent toll.^[14] Work on the Benedict Bridge began in May 1950.^[15] The toll plaza and administration building were completed on the Calvert County side of the bridge in autumn 1951. The bridge itself and 24-foot (7.3 m) wide gravel approach roads on both sides of the river were completed and opened in spring 1952.^[4] The toll was removed from the bridge in 1955 due to very low traffic; a daily average of 237 vehicles used the bridge in its first year.^[14][16] By comparison, the bridge had an average annual daily traffic figure of 12,312 vehicles in 2013.^[1]

The completion of the Benedict Bridge greatly improved the connection between Calvert County and both Charles and St. Mary's counties. Prior to 1952, the southernmost bridge on the Patuxent River had been Hills Bridge, by which MD 4 crosses the river at Upper Marlboro.^[17] By 1953, MD 231 between MD 5 in Hughesville and MD 2 in Prince Frederick was marked as a "main highway" on the state highway map.^[18] Reconstruction of MD 231 between MD 5 and MD 2 began in 1954. In both counties, the road was resurfaced in two stages: a first stage of bituminous stabilized gravel and a second stage of bituminous concrete.^[19][20] The reconstruction of MD 231 was completed from Prince Frederick to Hallowing Point in 1956 and from Hughesville to Benedict by 1958.^[20][21] The Benedict Bridge remained the southernmost crossing of the Patuxent River until the opening of the Governor Thomas Johnson Bridge between Solomons at the bottom of Calvert County and California in St. Mary's County in 1978.^[22] The "functionally obsolete" bridge underwent major repairs in 2002, during which the bridge was reduced to one lane of traffic in alternating directions.^[23][24]

•   Maryland Roads portal

• MDRoads: MD 231
• MD 231 at AARoads.com