Middlesbrough is a town in the Middlesbrough unitary authority borough of North Yorkshire, England. The town lies near the mouth of the River Tees and north of the North York Moors National Park. The built-up area had a population of 148,215 at the 2021 UK census. It is the largest town of the wider Teesside area, which had a population of 376,633 in 2011.Until the early 1800s, the area was rural farmland in the historic county of Yorkshire.