In 1938 the PO-Midi was nationalized with five other companies to become a part of the Société nationale des chemins de fer français (SNCF).

In addition, the company had one of the French government's awarded temporary concession of 70 years, to build and operate a railway between the cities of Paris and Orléans.

From the Gare d'Austerlitz, the network extended over the territory from the Loire and Garonne to Orléans and Tours.

From there, the branches led to Vendôme, Le Mans, the Atlantic coast of Angers, Nantes, St Nazaire to Landerneau, south of Villefranche, Clermont-Ferrand and Toulouse, south-west of Poitiers and Angoulême to Bordeaux.

To create an efficient, uniform and nationwide network under state control, on 1 January 1938, it was nationalized with five other companies to become a part of the newly founded Société nationale des chemins de fer français (SNCF).