The Compagnie de l'Ouest was created in 1855 by the merger of various small railway companies active in the western outskirts of Paris, in Normandy and in Brittany.

These were:[1] The Ouest's oldest line (still open to this day) is the line from Paris to Le Pecq, built by Émile Péreire's Compagnie du chemin de fer de Paris à Saint-Germain and inaugurated on 24 August 1837 by Marie-Amélie, wife of King Louis-Philippe.

The network was rapidly expanded:[2] To better use the Rive-Droite line, a 15 km (9 mi) long branch was built from Saint-Cloud to Saint-Nom-la-Bretèche at the cost of the French State.

L'Ouest built several stations within Paris; the two main terminals St Lazare and Montparnasse as well as Pont Cardinet at the beginning of the line to Auteuil.

More modest halts were graced with 'type' building, which are called 'type Ouest', the best-preserved examples can be found in Dives-sur-Mer and Houlgate.

As well as stations, infrastructure was also in mind when saving money so the Ouest created a level crossing guard house template (see below).

In 1893, Jean Jacques Heilmann [fr] built a steam-electric locomotive of Do Do wheel arrangement, which was trialled on the CF de l'Ouest.

Named La Fusée Electrique (English: The Electric Rocket), it was successful enough that two larger locomotives were constructed in 1897.