The South Durham & Lancashire Union Railway opened a single line between Barnard Castle and Tebay in 1861. It was taken over by the Stockton & Darlington Railway in 1863 and later the same year was absorbed by the NER. It was built to take coke to the Cumberland and Furness blast furnaces and to bring iron ore back to Cleveland; by 1874 much of the line was doubled. In 1910 five passenger trains were provided by the North Eastern Railway on weekdays, the journey taking 45 minutes. Forty years later the service was virtually the same.

Designed by the engineer Sir Thomas Bouch, Podgill Viaduct is about one and half miles east of Kirkby Stephen East Station and crosses the very attractive valley of Pod Gill down which flows the Ladthwaite Beck. It is built of local limestone and has eleven arches, each of 9 m. (30 ft.) span, giving it a total length of 142 m. (466 ft.), and a maximum height of 26 m. (84 ft.). Originally only 4 m. (12 ft.) wide between parapets for single track, it was built by contractors Chambers & Hilton at a cost of £6,189.

Doubling of the line between Kirkby Stephen and Belah, including the widening of Podgill Viaduct, was authorised by the directors of the North Eastern Railway on 5th September 1889, the work probably being completed about three years later. This task was undertaken by building a new, almost identical, viaduct alongside the existing, to which the new structure was tied.

Podgill Viaduct was acquired by the Northern Viaduct Trust direct from the British Rail Property Board in 2000

Merrygill Viaduct nerby spans the narrow valley of Hartley Beck which flows sharply down the western slopes Birkett Hill and through the village whose name the beck bears. Built of local limestone, Merrygill Viaduct has nine arches each of 9 m. (30 ft.) span, with a total length 111 m. (366 ft.), and a height above the beck of 24 m. (78 ft.). Like Podgill, it was originally built to carry only a single track, also being constructed by Chambers & Hilton for a price of £3,721.

Merrygill was widened to carry double track as part of the same contract for Podgill, completed about 1892. The ownership of Merrygill Viaduct had passed from British Railways to the owners and operators of Hartley Quarry, from whom it was acquired by the Northern Viaduct Trust in 2005.