Downtown Tulsa is in the northwest quadrant of the city and is ringed by an expressway called the Inner Dispersal Loop. Downtown's buildings include many large office towers. At , the BOK Tower (formerly One Williams Center) was the tallest building in any of the 5 "plains states" (Oklahoma, Kansas, Nebraska, North Dakota and South Dakota) until the Devon Tower in Oklahoma City was completed in 2012. The BOK Tower was designed in 1975 by Minoru Yamasaki & Associates, the same architect who designed the World Trade Center in New York City.