According to the SPV atlas, this line was originally the West Jersey & Seashore, later the Pennsylvania-Reading Seashore Lines, and more recently the northern portion was run by the Winchester & Western. The line roughly paralleled the eastern bank of the Maurice River, from Manumuskin south to the Delaware Bay at the small port town of Maurice River.
The rails are mostly still in place in the middle segment from Bricksboro south through Mauricetown to Dorchester, but they are severely deteriorated. The line was likely used to haul sand and gravel.
The line was likely abandoned in stages, from the 1950s to the 1980s. The first picture shows a paved-over grade crossing in Dorchester. The rails are intact on either side of the highway, but they are buried in thick brush. The second picture shows an abandoned crossing in Mauricetown Station.
Thanks to Mike Palmer for contributing information about this route.