National Road (US-40 / Alt-40 / I-68 corridor)

Maryland Route 135 stretches 29 miles from Oakland (US-219) in Garrett County east to McCoole (US-220) in Allegany County, crossing Backbone Mountain via a summit scenic overlook at 2,969 feet — the highest point on any Maryland state highway. The road traverses Potomac-Garrett State Forest along the ridgeline and drops steeply into the Bloomington area where it bridges the Savage River. It is part of the Mountain Maryland Scenic Byway. The Savage River Road spur off MD-135 near Bloomington adds short but exceptional forested twisties following the river downstream. The technical eastbound descent off Backbone Mountain is the most demanding section.

Maryland Route 77 runs 20.74 miles east-west through northern Maryland, ascending South Mountain before descending Catoctin Mountain along the narrow Hunting Creek valley. The road threads between Cunningham Falls State Park to the south and the National Park Service-managed Catoctin Mountain Park to the north — the same forested ridge sheltering Camp David. The highway is designated as both the Journey Through Hallowed Ground Byway and the Old Main Streets Scenic Byway, and passes through Thurmont (junction with US-15) before extending east through Rocky Ridge to Keymar. Densely forested twisties through the park corridor are the draw; fruit stands and a covered bridge punctuate the quieter eastern farmland section.

Maryland Route 550 runs 24.43 miles from Libertytown north to Fort Ritchie (Pen Mar Road), linking Frederick and Washington counties through a mix of open Monocacy Valley farmland and forested Catoctin and South Mountain terrain. The highway connects Woodsboro, Creagerstown, Thurmont, and Sabillasville, passing along the northern edge of Catoctin Mountain Park before cresting South Mountain near the Pennsylvania state line at Blue Ridge Summit. It is part of the Journey Through Hallowed Ground Byway. Fruit stands, 18th-century farmhouses, and the Victor Cullen Center dot the roadside; the northern stretch becomes genuinely mountainous as it approaches Pen Mar County Park. Pairs well with MD-77 and MD-491 for a natural Catoctin-South Mountain loop.