Libertytown to Thurmont

View north along MD 550 just north of Creagerstown

MD 550 begins at an intersection with MD 26 (Main Street) in the unincorporated village of Libertytown and heads northwest as Woodsboro Road.^[2] The highway passes through the Piedmont uplands, a region of rounded hills, low ridges, relatively high relief, irregular plains, and narrow valleys with a mix of farms and forests.^[3][4] MD 550 crosses Cabbage Run and Dorcas Branch, follows Dorcas Branch through a gap in Laurel Hill, and enters the town of Woodsboro just after crossing Israel Creek. MD 550 turns north and runs concurrently with MD 194 on Woodsboro Pike on the east side of the town; Liberty Road heads west from the intersection toward the center of town. ^[2][5] MD 550 turns west onto Woodsboro–Creagerstown Road, which immediately intersects the north end of Main Street (MD 194A).^[1][2] The state highway intersects the MDOT Branch of the Maryland Midland Railway and receives the north end of Creagerstown Road before leaving Woodsboro.^[2][6]

MD 550 continues northwest through the Piedmont lowlands, which contain wide and undulating ridges, broad nearly level valleys, limited local relief, and a mosaic of farms, houses, and woodland.^[3][4] North of the route's bridge across the Monocacy River, the highway parallels Pennterra Manor Lane, which leads to the 18th century farmhouse Pennterra.^[2][7] MD 550 also passes to the west of another 18th century harmhouse, Strawberry Hill, before reaching the unincorporated village of Creagerstown.^[2][8] The route’s name changes to Creagerstown Road at Old Frederick Road at the south end of village, and at Blacks Mill Road the road passes to the east of the St. John's Church at Creagerstown Historic District, which preserves a pair of church buildings—the early 20th century St. John’s Evangelical Lutheran Church and the 19th century building of the defunct St. John’s Reformed Church—as well as the first church’s parish house and a cemetery.^[2][9] MD 550 continues northwest as Creagerstown Road to the hamlet of Jimtown; the highway intersects Moser Road and Hessong Bridge at a four-legged intersection and turns north onto Jimtown Road toward Thurmont.^[2]

View south along MD 550 from US 15 in Thurmont

MD 550 enters the town of Thurmont just before the highway intersects MD 77 (Rocky Ridge Road). The two state highways run concurrently northwest toward downtown Thurmont on Main Street. In the center of town, at Water Street, MD 77 continues west on Main Street while MD 550 turns north onto Church Street, which passes under the Main Line of the Maryland Midland Railway and meets the south end of MD 806 (Emmitsburg Road).^[2][10] At the northern edge of Thurmont, the state highway meets US 15 (Catoctin Mountain Highway) at a diamond interchange and passes Catoctin High School.^[1][2]

Thurmont to Highfield–Cascade

MD 550 heads northwest as Sabillasville Road into the Blue Ridge Mountains, which comprise extensively forested, steep, and well-dissected ridges separated by deep, narrow valleys with patches of farmland.^[2][3][4] The highway crosses Owens Creek and parallels the Maryland Midland Railway through the creek’s gorge upstream between Piney Mountain to the north and Catoctin Mountain to the south; the highway passes under the rail line twice. At Foxville Deerfield Road, MD 550 leaves Owens Creek and its gorge and passes through the Harbaugh Valley, where the highway crosses Friends Creek.^[2][11] After passing through the unincorporated village of Sabillasville and intersecting Bentzel Road on the north side of the village, the highway leaves the valley and ascends the eastern flank of South Mountain.^[11] MD 550 passes under a curve of the railroad and meets the ends of Old Sabillasville Road and Cullen Drive west of the Victor Cullen Center.^[1][2] The Victor Cullen Center is a state youth detention center originally constructed in the first decade of the 20th century as the state’s first tuberculosis sanatorium, whose preserved historic remains include the power house and old administration building.^[12][13][14]

MD 550 curves west parallel to the Maryland Midland Railway and summits South Mountain at the Frederick–Washington county line about 400 feet (120 m) south of the Pennsylvania state line.^[11] The highway continues as Fort Ritchie Road, which curves southwest through the unincorporated communities of Highfield and Cascade, where south of Royer Road the route’s name changes to Military Road. At the entrance to the former Fort Ritchie, MD 550 meets the northern end of MD 491 (McAfee Hill Road) and turns northwest onto that road.^[2][15] The highway intersects CSX's Hanover Subdivision rail line at grade, turns from McAfee Hill Road onto Pen Mar Road, and passes under the railroad and by Lake Royer.^[2][16] MD 550 reaches its northern terminus west of the lake at the edge of Camp Louise, a girls' summer camp founded in 1922; Pen Mar Road continues as a county highway toward the community of Pen Mar and Pen Mar Park.^[2][15]