Maryland Route 400 was the designation for Mount Wilson Lane, which ran from MD 140 west to the Western Maryland Railway (now CSX's Hanover Subdivision) and the former Mount Wilson Hospital Center near Garrison in western Baltimore County.

[7] Maryland Route 403 was the designation for what was then named Colesville Road, which ran from MD 500 in Hyattsville east to US 1 in Riverdale in northern Prince George's County.

[11] Maryland Route 406 was the designation for Rehobeth Road from MD 667 at Hudson Corner east to US 13 in West Pocomoke in southern Somerset County.

[6] The highway received an underpass of the Baltimore & Ohio Railroad (now CSX's Philadelphia Subdivision) and approaches to the grade separation in 1939.

[2][19] MD 409 was extended east through the I-83 interchange after the freeway was built between Parkton and the Pennsylvania state line in 1958 and 1959.

[21] The portion of Rhode Island Avenue from the District of Columbia east to 38th Street was built as a concrete road as part of MD 206 between 1916 and 1919.

[2][19] By 1934, the 20-foot-wide (6.1 m) highway was proposed to be expanded to 40 feet (12 m) because it carried an average of 19,105 vehicles per day.

[10] Maryland Route 416 was the designation for Southern Maryland Boulevard from MD 2 in Sunderland north to MD 4 at Waysons Corner in northern Calvert County and southern Anne Arundel County.

[35] Maryland Route 417 was the designation for Springs Road from US 40 (now US 40 Alternate north to the Pennsylvania state line in Grantsville in northern Garrett County.

[29] Maryland Route 419 was the designation for a pair of highways near Dickerson in western Montgomery County.

[32] Maryland Route 426 was the designation for Liverpool Point Road from the Potomac River east to MD 6 in Nanjemoy in western Charles County.

[10] Maryland Route 427 was the designation for Chapel Point Road, which ran from the Port Tobacco River in Chapel Point State Park east to US 301 at Bel Alton in southern Charles County.

[32] Maryland Route 433 was the designation for Powder Mill Road on both side of US 1 in Beltsville in northern Prince George's County.

[5] The route was relocated just east of US 1 when Powder Mill Road was placed on its present bridge across the Baltimore & Ohio Railroad (now CSX's Capital Subdivision) in 1939.

MD 435 used Annapolis Street and Severn Avenue south and east of the intersection, respectively.

[MD 442 1] Maryland Route 443 was the designation for Still Pond Neck Road, which ran 0.88 miles (1.42 km) from MD 292 near Betterton west to Clark Road at the hamlet of Coleman in northern Kent County.

[MD 448 1] Maryland Route 449 was the designation for Aiken Avenue Extended and Clayton Street, which spanned 0.53 miles (0.85 km) in Perryville in western Cecil County.

Aiken Avenue Extended ran from US 222 (now MD 222 at that highway's modern intersection with US 40 north to the Baltimore & Ohio Railroad (now CSX's Philadelphia Subdivision), and Clayton Street extended from the railroad northeast to US 222.

[24] Maryland Route 467 was the designation for Delmar Road from MD 313 near Mardela Springs east to the Maryland–Delaware state line in northwestern Wicomico County.

[46] The first section was constructed as a macadam road by Caroline County with state aid from the Maryland, Delaware & Virginia Railroad just east of the town of Denton along what is now Market Street east to Garland Road by 1910.

[37] Maryland Route 475 was the designation for Jacksonville Road north from MD 413 near Crisfield in southern Somerset County.

This four-lane portion of East Street crosses Carroll Creek and provides access to the Frederick terminal station of MARC's Brunswick Line.

[62] MD 475 was transferred to city maintenance after the extension of East Street and the single point urban interchange at I-70 were completed and opened in December 2009.

[5] In 1952 and 1953, part of the highway was temporarily a piece of US 40 when Baltimore National Pike (now I-70) was finished east of MD 476 yet under construction to the west.

[10] Maryland Route 477 was the designation for Old Washington Road, which ran from US 1 near Montgomery Road south of Elkridge north to US 1 just south of the U.S. Highway's underpass of the Baltimore & Ohio Railroad (now CSX's Capital Subdivision) in Elkridge in eastern Howard County.

[22] This expansion quickly became obsolete, so between 1928 and 1931, newly designated US 1 was expanded from 20 to 40 feet (6.1 to 12.2 m) over its entire length and relocated to its present alignment through Elkridge.

[65][4] Maryland Route 479 was the designation for the access road from US 50 to the former Eastern Shore State Hospital in Cambridge.

[7] The highway had previously also included Poorhouse Road from Pisgah east to MD 6 near Port Tobacco.

[31] The highway was constructed as a gravel road for 1 mile (1.6 km) north from the Nanjemoy end in 1933.

[10] Maryland Route 492 was the designation for Maryland Park Drive from the District of Columbia boundary at 63rd Street and Southern Avenue east to MD 214 near Capitol Heights in central Prince George's County.