The history of the line began in 1866. The "Compagnie des Dombes et des Chemins de Fer du Sud Est" (DSE), founded 1863, obtained a concession to build and operate a line linking the communes of Bourg-en-Bresse and La Cluse. This project, deemed insufficiently lucrative by the major companies was given life thanks to a law passed in 1865 allowing lines 'of local interest' to be financed by departments and municipalities. However work only began in September 1872 after delay caused by a conflict in 1870 with the (PLM) with which the DSE was becoming a serious competitor. The outcome was a requirement to share stations with existing ones on the network and to use standard gauge track to ensure interoperability.