Over the years, Oswego has been the site of four lighthouses. The first lighthouse was built in 1821 on the grounds of Fort Ontario and discontinued in 1838. After the completion of the West Harbor Pier in 1836 (running west to east from Third Street), a limestone tower light was built at its eastern end. The tower was raised 25 feet in 1868 and designated the Inner Harbor Light.
In 1869, the pier was extended northward from its eastern terminus, forming an elbow with its northernmost point, identified with an iron lighthouse. In 1881, after the completion of the outer west breakwater, making an enclosed harbor, the lighthouse was moved to the end of the breakwater and designated the Outer Harbor Light.
By 1931, both the lighthouses and the inner pier were gone, three years later the pierhead lighthouse, which exists today, was built.