The Liskeard and Caradon Railway was opened on 28 November 1844 from quarries on the moors north of Liskeard to Moorswater where goods were transhipped to the Liskeard and Looe Union Canal. At Looe they could then be transhipped again to sea-going vessels for transport further around the coast.

The canal was superseded by a railway on 27 December 1860 and passengers were carried on the Moorswater to Looe section from 11 September 1879. The Cornwall Railway, which was the predecessor of the GWR, opened in 1859, and had intended to make a junction with the Liskeard and Caradon Railway near Moorswater, but a lack of capital saw this scheme abandoned, the line passing high above the goods yard on the Moorswater Viaduct. The new station, which was situated just north of the viaduct, was used by passengers travelling into Liskeard, but from 1896 a platform was provided at Coombe where trains would call to set down passengers going to Liskeard railway station if they notified the guard, as the steep road from there to the station was considerably shorter than the route from Moorswater.

The viaduct was 45 m (147 ft) high, 291 m (954 ft) long on 14 piers. In 1855 two of the piers then under construction collapsed. Brunel inspected them and rebuilt them the following year to his original design but with timber reinforcement. The viaduct carried a single broad gauge track. Six of the piers still stand beside the replacement bridge. They were buttressed at each end so were double cruciform in section. In the main body of each there were four tiers of gothic arches. The track was supported by a fan-like timber structure, and it is said that the whole creaked and vibrated when trains were crossing at speed.

It was replaced by a new stone viaduct with cast iron parapets on 25 February 1881. This is the largest of the conventional viaducts and is generally held to be the most attractive. The line that runs below the viaduct is the Liskeard and Looe Railway.