One of the largest expanses of extensive green roof is to be found in the US, at Ford Motor Company's River Rouge Plant, Dearborn, Michigan, where of assembly plant roofs are covered with sedum and other plants, designed by William McDonough; the $18 million assembly avoids the need of what otherwise would be $50 million worth of mechanical treatment facilities on site. Built over Millennium Park Garage, Chicago's Millennium Park is considered one of the largest intensive green roofs. Other well-known American examples include Chicago's City Hall and the former Gap headquarters, now the headquarters of YouTube, in San Bruno, CA. The U.S. military has two major green roofs in the Washington, D.C. area: the U.S. Coast Guard headquarters () and the Pentagon ().