The old alignment of US 40 through Frederick begins at a partial cloverleaf interchange with the Frederick Freeway, which heads north from the interchange as US 15 and south as a concurrency of US 15 and US 40. Patrick Street heads east from the interchange as a four-lane undivided highway that splits into a one-way pair just beyond Catoctin Street. The eastbound direction, which is signed as eastbound MD 144 at the split, follows municipally-maintained South Street. MD 144 in Frederick officially begins at the intersection of Patrick Street, which is one-way westbound, and Jefferson Street, which was formerly US 340. Both streets pass through the Frederick Historic District: Patrick Street crosses Carroll Creek into the commercial district, while South Street has a more residential flavor. Both streets intersect Market Street, the main north–south thoroughfare of the downtown area that was formerly MD 355. The eastbound direction of MD 144 turns north onto East Street, passing by the Frederick station serving the Frederick Branch of MARC's Brunswick Line and traversing Carroll Creek before meeting Patrick Street.