But it isn't and won't be the largest house in America. That title is held by the Biltmore Estate at a mere 175,000 square feet. And yes, it is still privately owned by the Vanderbilt family. These people have been working on this house for years now and say "if the money holds out?" Apparently they don't have it to spend if money is a concern. The Vanderbilts built an entire town and rail line just to build their house. Now that is wealth.