In 1871, following the French defeat in the Franco-Prussian War and the signing of the Treaty of Frankfurt, Raon-lès-Leau and its close neighbour Raon-sur-Plaine were initially annexed by Prussia, along with the rest of Alsace-Lorraine.

However, due to repetitive protests from the local population, the two villages were soon returned to France, but not without the loss of most of their surrounding forests, which the Germans intended to keep as a glacis for the defensive position of Mont Donon.

These terms were accepted by the French government which was desperately trying and more focused on retaining territorial control of a private railway line at Avricourt.

Opinions vary as to which nation state benefited from this last minute revision of the Treaty of Frankfurt, but for the villagers stripped of most of their rich forests, the deal was poor.

Most of the woodland which before 1871 belonged to Raon-sur-Plaine and Raon-lès-Leau an thus to Lorraine therefore remains, since that date, a part of Grandfontaine in Alsace.