By the Seashore was created in 1883.
Conway Seashore Railroad was created in 1899.
Canaveral National Seashore was created on 1975-01-03.
Delaware Seashore State Park was created in 1965.
Assateague Island National Seashore was created in 1965.
Padre Island National Seashore was created on 1962-09-28.
Cape Cod National Seashore was created on 1961-08-07.
Gulf Islands National Seashore was created on 1971-01-08.
Fire Island National Seashore was created on 1964-09-11.
Cape Lookout National Seashore was created on 1966-03-10.
Point Reyes National Seashore was created on 1962-09-13.
Cape Hatteras National Seashore was created on 1953-01-12.
No, seashore is a noun.