Quadrangle Development Corporation is a privately held, vertically integrated real estate development company based in Washington, D.C., in the United States. By 2002, it was one of the largest real estate developers in the Washington, D.C., metropolitan area. As of April 2011, the company owned 83 properties (consisting of apartment buildings, condominiums, hotels, and office buildings) totaling 22,000,000 square feet (2,000,000 m2) and worth $8.4 billion.