Windsor Ruins are in Claiborne County, Mississippi, United States, about 10 miles (16 km) southwest of Port Gibson near Alcorn State University. The ruins consist of 23 standing Corinthian columns of the largest antebellum Greek Revival mansion ever built in the state. The mansion stood from 1861 to 1890, when it was destroyed by fire. The 2.1-acre (0.85 ha) site was added to the National Register of Historic Places in 1971 and was designated a Mississippi Landmark in 1985.