Tulsa is the second-largest city in the State of Oklahoma and 47th-most populous city in the United States. A building boom in the early 20th century gave Tulsa one of the largest concentrations of art deco architecture in the United States. The city's historical residential core lies in an area known as Midtown. The University of Tulsa, the Swan Lake neighborhood, Philbrook Museum, and the upscale shopping districts of Utica Square, Cherry Street, and Brookside are located in this region. This region, marked by secluded homes and suburban neighborhoods, contains one of the state's largest shopping malls, Woodland Hills Mall.