In 1778, the Cann Slate Quarry was owned by John Parker, and in order to make transport of the slate easier, he asked the engineer John Smeaton to survey a canal, to run from the quarry to the bridge at Marsh Mills.

Although Smeaton carried out the work, he concluded that the canal, which would be 2.25 miles (3.62 km) long and would need several locks to accommodate the drop of 30 feet (9.1 m) in level, was unlikely to be economic, since the only trade would be the output from the quarry.

In 1821, the directors of the Plymouth and Dartmoor horse tramway applied for a second act of Parliament, the Plymouth and Dartmoor Railway Act 1821,to authorise a deviation to the route, and in order to obtain consent for the new route from Parker's son, also called John Parker and Earl of Morley since 1815, they agreed to build a branch, possibly including an inclined plane, to the quarry.

Despite the fact that he was a member of the management committee for the tramway, Parker took legal action against the three directors who had proposed the branch.

They suggested that he should build the branch himself, and in return, all goods transferring from it to the existing tramway would be subject to lower tolls.

The current Marsh Mills Station is a little further to the north than the original one, as a mineral line which serves a china clay works still passes through the old site.

The railway crosses the route of the canal in two places on this section, and both of the bridges have been rebuilt as part of the restoration.