[3] Maryland Route 503 was the designation for Olivet Road from the community of Olivet at the confluence of Mill Creek and St. John Creek north to MD 2 (now MD 765) near Lusby in southern Calvert County.
[5] MD 504 was resurfaced in 1944 due to being the access road to a U.S. Navy amphibious base.
[7] Maryland Route 511 was the designation for Parkers Wharf Road from near the Patuxent River north to MD 264 near Mutual in southern Calvert County.
[7] Maryland Route 512 was the designation for Williams Wharf Road from near the Patuxent River east to MD 264 near Mutual in southern Calvert County.
[7] Maryland Route 513 was the designation for Piney Branch Road from the Washington, D.C., boundary in Takoma Park north to MD 320 in Silver Spring in southeastern Montgomery County.
[3] Maryland Route 516 was the designation for Franklin Avenue from US 29 east to MD 193 within Silver Spring in southeastern Montgomery County.
[21] MD 526 was assigned to Pennsylvania Avenue after US 140 was moved to the Westminster Bypass when it opened in 1954.
[MD 530 1] These two blocks of Cross Street were brought into the state highway system by 1939.
[12] The first portion of the Carroll County segment was built as a concrete road east from Mount Airy in 1933.
[4] Maryland Route 537 was the designation for Daves Hill Road, which ran 0.71 miles (1.14 km) between intersections with MD 213 on either side of Woodland Creek west of Galena in northeastern Kent County.
[4] Maryland Route 548 was the designation for Upper Ferry Road from MD 529 (now Allen Road) at Allen north to the south port of the Upper Ferry on the Wicomico River in southern Wicomico County.
[12] The first segment of the highway was built as a macadam road a short distance north from Allen in 1933.
[4] Maryland Route 554 was the designation for a pair of highways in Severn in western Anne Arundel County.
The designation was originally assigned to Telegraph Road from Odenton north to the MD 170–MD 174 intersection in Severn.
At that time, MD 170 turned west at Severn to head toward Fort George G.
[31] Maryland Route 555 was the designation for Wilson Road from MD 263 at Plum Point south a short distance in central Calvert County.
[31] The first segment of the highway was built as a concrete road from MD 214 north to near the hamlet of Woodmore in 1933.
[32] Maryland Route 558 was the designation for Bel Alton Newtown Road from MD 3 (now Fairgrounds Road) northeast to MD 6 at the hamlet of Newtown southeast of La Plata in southern Charles County.
[12] The first segment of the highway, from MD 3 to near Clark Run, was completed as a gravel road in 1933.
[4] Maryland Route 570 was the designation for a pair of stretches of Old Washington Road in southern Carroll County.
[4] Maryland Route 573 was the designation for Bartholow Road on either side of Little Morgan Run near Eldersburg in southeastern Carroll County.
[31] Maryland Route 575 was the designation for Pond Woods Road from MD 2 north of Huntingtown east toward Willows in northern Calvert County.
[36] The highway was constructed as a macadam road for a short distance south from MD 371 in 1935.
[18] The highway was constructed by Somerset County with state aid as a 12-foot-wide (3.7 m) macadam road by 1915.
[12] The highway was constructed as a macadam road from MD 12 to the site of what is now Salisbury–Ocean City–Wicomico Regional Airport in 1935.
[4][38] Maryland Route 590 was the designation for Forge Hill Road from US 1 near Kalmia north to US 1 near Dublin.
[43] After US 1 was relocated on either side of Deer Creek to its present course in 1934, MD 590 was applied to the old highway.
[12] Maryland Route 592 was the designation for the 0.23-mile-long (0.37 km) stretch of Sylmar Road from MD 273 north to US 1 near Rising Sun in northern Cecil County.
[38] Maryland Route 597 was the designation for Forest Glen Road from Dallas Avenue east to US 29 in Silver Spring in southeastern Montgomery County.
[36] The highway was constructed as a 12-foot-wide (3.7 m) macadam road from Princess Anne to Kings Creek in 1911.