Pierre Léger Prosper Allemand was born on 16 July 1815 in Allemagne, Basses-Alpes (now Alpes-de-Haute-Provence).

[1] His parents were Jean François Allemand (1775–1836), a health officer and mayor, and Marie Élisabeth Poitevin.

[2] Allemand joined in the rebellion against the coup d'état of 2 December 1851, along with Charles Cotte and Marius Soustre.

He ran for the Chamber of Deputies on 20 February 1876 for the Digne constituency and won by 7,643 votes against 2,953 for the Bonapartist Falcon de Cimier.

He voted for the partial amnesty, for invalidation of the election of Louis Auguste Blanqui, for application of existing laws to unauthorized congregations and for divorce.

[1] On 6 September 1909 Aristide Briand presided over the inauguration of a bust of Allemand in Allemagne-en-Provence by Jeanne Royannez(fr), wife of Clovis Hugues.