The Largest Historic Homes In The United States

In 2009, the median size of new homes started was roughly 2,100 square feet. This figure was down from 2,200 square feet between 2005-2007 which, itself, was down from 2,350 in 2004.
Homes are getting smaller across the United States.
But, as compared to the nation's largest homes, the shrinking is laughable. The Biltmore Estate, built in 1895 by George Washington Vanderbilt II, measures 175,000 square feet -- 83 times the size of a typical home today.
The Biltmore Estate in Asheville, North Carolina is the largest home in the country and, meanwhile, another Vanderbilt-built property built in 1895 checks in at number two. The Breakers, in Newport, Rhode Island, measures 165,000 square feet and cost $150 million to build in today's dollars, adjusted for inflation.
Both homes are open to the public.
The next three largest U.S. estates in terms of square footage are:

• Oheka Castle in Huntington, New York (109,000 square feet)
• Winterthur in Winterthur, Delaware (96,582 square feet)
• Meadow Brook Hall in Rochester Hills, Michigan (88,000 square feet)

Hearst Castle, arguably the most famous "large home" in the country, measures 60,645 square feet and ranks 7th.
See the complete list of Largest Historic Homes In The United States, including their build date and architecture style, on Wikipedia.