The Royal River in Yarmouth empties into Casco Bay, about 11 miles north of Portland Harbor. It is used by fishing and recreational craft. Two boatyards and a crabmeat packing plant are located near the head of the project in Yarmouth.

Initial work on the river, completed in 1883, consisted of constructing a channel, 4.5 feet deep and 100 feet wide, to the head of commercial navigation at what is now U.S. Route 95. This included removing obstructions on the bar at Gravel Point, about 0.5 mile downstream of the present highway, and several ledges near the commercial wharves at Yarmouth. A 195-foot-long stone jetty was constructed on the river’s south bank, opposite Wolfe’s Point, about 0.8 mile from its mouth.

In 1967, the Corps completed additional work in the harbor under Section 107 of the Continuing Authorities Program. It consisted of an eight-foot-deep channel, 80 feet wide, extending about three miles from the deep water in Casco Bay to the commercial wharves at Yarmouth; and a six-foot-deep anchorage, eight acres in area, at the wharves.