The pillars are all that's left of the Windsor Ruins, a mansion that was built just prior to the Civil War and completely destroyed in a fire in 1890.
The 17,000 square foot mansion with 29 forty foot tall columns was built 4 miles east of the Mississippi River on a 2600 acre cotton plantation by Smith Daniel who died just after its completion at the age of 34. The mansion was used by Ulysses S. Grant during the war as a command post. In today's currency, the mansion would have cost nearly 5 million dollars to complete. The property remained with the family until 1974 when they donated the site to the state of Mississippi.