The archives of two Roman Catholic congregations of French origin which have missionaries in Gabon are located in Rome: the Sisters of Our Lady of the Immaculate Conception of Castres (commonly called the Blue Sisters) and the Brothers of Saint Gabriel of Saint Laurent-sur Sèvres. The Blue Sisters were founded by Emilie de Villeneuve in 1836 to improve the condition of women, in particular by educating poor and orphaned girls. The Brothers of Saint Gabriel were organized by Louis Grignion de Montfort in 1715 to provide a primary education for poor boys and were reorganized in 1821 by Gabriel Deshayes. Initially both congregations worked only in France. They entered Gabon at the request of the Holy Ghost Fathers-the sisters in 1849 and the brothers in 1900. The sisters had communities at most of the mission stations--in the Estuary at first and from the 1880s along the Ogooué river and other points in the interior. The brothers operated schools at Libreville and Lambaréné, and after the Second World War at Port-Gentil and Oyem as well. During the past century both congregations became primarily missionary bodies, with the sisters active in Africa and South America and the brothers in Africa, Asia, and the Pacific. These international activities led to the transfer of their headquarters to Rome in the 1950s.

The sisters who worked in Gabon prior to the Second World War included many with intelligence but few with much formal education beyond the primary grades. They spent their time in social service, health care, and elementary education. The latter included French as well as religion and the domestic arts. The sisters had much less contact with the government or the colonial administration than did the Holy Ghost Fathers, who were their ecclesiastical superiors. Though some sisters toured to provide medical aid to persons away from the mission stations, most of their contacts with Africans took place in or near the stations.