In 1858, a 6 kilometres (3.7 mi) standard gauge branch to St. Valery Quai was opened.

A 6 kilometres (3.7 mi) extension to Le Crotoy opened on 1 July 1887.

A 19 kilometres (12 mi) metre gauge line to Cayeux-sur-Mer opened on 6 September 1887.

[2] On 28 August 1892, an 11 kilometres (6.8 mi) metre gauge line opened to Forest-l'Abbaye, joining with a 42 kilometres (26 mi) long line between Abbeville and Dompierre-sur-Authie which had opened on 19 June 1892.

[2] The standard gauge line to St. Valery was operated by SNCF until 6 February 1989 and officially closed from 1 January 1993.