Ernest Whitworth Marland Mansion - Credit: Wikimedia Commons
The E.W. Marland Mansion is a Mediterranean Revival-style mansion located in Ponca City, Oklahoma, United States. Built by oil baron and philanthropist Ernest Whitworth (E.W.) Marland, as a display of wealth at the peak of the 1920s oil boom, the house is one of the largest residences in the southwestern United States, and is known as the "Palace on the Prairie." It was designated a National Historic Landmark in 1973, and is now a museum open to the public. Read more on Wikipedia
Source: en.wikipedia.org