Darlington is a large market town in the ceremonial county of Durham, in the city-region of the Tees Valley and in North East England. With a population of 105,564 in 2011, the town lies on the River Skerne, a tributary of the River Tees. The town is administered as part of the Borough of Darlington. The town owes much of its development to the influence of local Quaker families in the Georgian and Victorian era, and who provided much of the finance and vision in creating the Stockton and Darlington Railway, the world's first steam locomotive powered, permanent passenger railway. The town is often colloquially referred to as 'Darlo'.