Southwest Ledge Light guards the main entrance to New Haven Harbor from a hazardous underwater ledge along the channel’s eastern side. Built between 1873 and 1877, it was among the first lighthouses erected on a cylindrical iron foundation, a design developed by Maj. George H. Elliot to withstand shifting ice and important to later lighthouse engineering. Its three-story octagonal, Second Empire structure combines cast-iron exterior detailing with wood-framed interior rooms. Reinforced in 1911 and automated in 1973 after decades of staffed service, it remains an active navigational aid, was listed on the National Register of Historic Places in 1990, and was acquired in 2016 by Dr. Casey Jordan of Beacon Preservation, Inc.