Known as Mountain Road, the highway runs 10.92 miles (17.57 km) from MD 2 in Pasadena east to Gibson Island.

MD 177 serves as an arterial highway through Pasadena, Jacobsville, and the Lake Shore area of northeastern Anne Arundel County.

MD 177 continues east as a two-lane undivided road that regularly gains a center left-turn lane.

The state highway intersects another section of MD 648 (Waterford Road), Catherine Avenue, and Edwin Raynor Boulevard on its way to Jacobsville.

The eastern end of the three-lane section is at South Carolina Avenue in the community of Lake Shore.

At Pinehurst Road, which leads to Downs Memorial Park, the route veers southeast toward Gibson Island.

MD 177 reaches its eastern terminus at the gatehouse that guards the private island community on the north side of the mouth of the Magothy River at the Chesapeake Bay.

[16] In 1966, the freeway was extended slightly east to terminate at Mountain Road at an intersection at the site of today's ramps to and from westbound MD 100.

[22] Since the late 1970s, heavy traffic on MD 177 east of MD 100 has spurred efforts to build a bypass of the Lake Shore section or widen the highway, projects that have been opposed by residents who fear increased development on the peninsula.