Plano is a city in the U.S. state of Texas, located twenty miles northeast of downtown Dallas. The city of Plano is a part of the Dallas-Fort Worth metropolitan area. Plano lies mostly within Collin County, but includes a small portion that extends into Denton County.The city's population was 269,776 at the 2010 census, making it the ninth most populous city in the state of Texas and the 69th most populous in the United States. The city is a hub for many corporate headquarters.