The Tanfield Waggonway was built by the Grand Allies from about 1720 to transport coal more reliably & cheaply from inland collieries of County Durham, to the staiths on the River Tyne at Redheugh. From here the coal was transported in keels downriver to South Shields, then transferred to colliers (bulk coal carrying ships) for the voyage down the North Sea coast to south east England.
Many older shorter coal waggonways existed to the north of the present heritage line, in the Whickham & Lobley Hill areas, but the Tanfield Waggonway was a much longer and heavily engineered route which gave the Grand Allies market dominance all year round. Although supply to SE England was still subject to North Sea winters.
The Tanfield route was in continuous use from 1725 until final closure in 1964, though the Tanfield Railway still uses some of that infrastructure today, nearly 300 years later.