This branch line was opened in 1846 and carried passengers and farm produce from Haddington and the surrounding area to Edinburgh. In return the railway transported horse dung from the streets of Edinburgh to be used on the East Lothian farms! The passenger service was closed in 1949 due to increased use of buses and cars, with freight trains continuing until the closure of the line in 1968.

The total distance of the route is four and a half miles (7 km) between Longniddry and Haddington. The route is fairly level with only gentle inclines and a firm surface. There are small car parks at Longniddry and Cottyburn and access can be gained at several points in Haddington.

Currently there are locked gates at various entrance points to prevent vehicular access to the railway line. Horse-riders can contact the Landscape and Countryside Department of the Council for a key. This route offers access to parts of East Lothian that can't be reached by car. The hedgerows and woodland along the route offer shelter to a great diversity of wildlife and many rare wild flowers are established along the embankments.