In 1855 the West Somerset Mineral Railway Act incorporated the company and gave permission for the construction of a line from Watchet Harbour through Roadwater through to Brendon Hill to a terminus near Heath Poult Cross.
Building works formally started with the turning of the first sod in May 1856 and were completed in 1864.
There was only one feasible route from Watchet to Roadwater, following the valley of the Washford river, but from Roadwater on two possible routes were being considered.