At 90,000 square feet, The American Versailles — the dream of time-share mogul David Siegel and his wife Jackie — would have been the third largest private home in America. Economic realities have put a stop on construction, but Lauren Greenfield's summer documentary The Queen of Versailles has thrust the home, and the spirit of American access, into the spotlight.
Large homes are a hallmark of America's 1%. Gilded Age Barons in Newport, Rhode Island set a standard. A small part of all super-rich all Americans still wants to trump their predecesors.
Our survey of the largest homes excludes some of the most famous ones, like the Breakers, as they now serve as house museums. Others, still in their construction phase, are ignored, because they do not have inhabitants. Instead we focus on the mega-mansions that are first and foremost private homes. Some are owned by celebrities, and others are owned by oligarchs. All of them have space, and lots of it. 
There's no house under 40,000 square feet, and there are hardly any without private bowling allys. 

The 25 Largest Homes In The United States