Windsor Ruins are in Claiborne County, Mississippi, United States, about 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 site with the columns was added to the National Register of Historic Places in 1971 and was designated a Mississippi Landmark in 1985. He was born in Mississippi and had acquired great wealth by age 30 as a cotton planter. In 1849, Smith Daniell married his cousin Catherine Freeland (1830–1903).

The footprint for Windsor mansion was set by 29 columns which supported a projected roof line that protected wide verandas on the second and third floors. Following the Battle of Port Gibson, the mansion was used by Union troops as a hospital and as an observation station. The Daniell family was allowed to live on the third floor of the mansion during the Union occupation. Historians believe that Henry Dwight made the sketch while his unit was encamped on the grounds of the mansion. Windsor mansion was destroyed leaving only the columns, balustrades, cast iron stairways, and pieces of bone china.

Through the years, three of the cast iron stairways, that survived the 1890 fire, disappeared from the site.

North of Windsor Ruins is a cemetery where members of the Daniell and Freeland families have been buried since the early 19th century. The earliest grave is that of Frisby Freeland (1747 – 1819), an American Revolutionary War soldier.

Windsor's ruins have been shown in two motion pictures—Raintree County (1957) and Ghosts of Mississippi (1996).