Known as Whites Neck Road, the state highway runs 2.61 miles (4.20 km) from a dead end at a boat ramp north to MD 239 near Bushwood in western St. Mary's County.

MD 520 begins at a boat ramp at the southern end of Whites Neck adjacent to the mouth of Whites Neck Creek at St. Catherine Sound, an embayment of the Wicomico River.

The 18-foot (5.5 m) wide two-lane undivided state highway heads west then north through farmland.

MD 520 veers northeast through a forested area before crossing Whites Neck Creek and reaching its northern terminus at MD 239 (Bushwood Wharf Road) near the community of Bushwood.

[3] The state highway was widened and resurfaced with bituminous concrete in 1956.