Hearst Castle, California

William Randolph Hearst's estate at San Simeon, designed by architect Julia Morgan and built between 1919 and 1947, was the largest private home in the United States during its construction. The 90,080 square foot main house (Casa Grande) contains 38 bedrooms, 41 bathrooms, and houses a collection of European art and antiquities valued in the hundreds of millions. It is now a California State Historic Park.