Old Salem County Courthouse, New Jersey. Built in 1735, this building is the oldest active courthouse in New Jersey and is the second oldest courthouse still in continuous use in the United States. It was built using locally manufactured bricks and was enlarged in 1817 and 1908. It served as the courthouse for Salem County until 1969 when a larger and more modern facility was built for the county. Today it serves as the courthouse for the Salem City Municipal Court.