Music teacher and civil rights activist Delphine “D.J.” Dupuy was one of the founding members of the Baton Rouge branch of the National Association for the Advancement of Colored People (NAACP) in 1929. She held various elected posts in the branch for more than fifteen years, serving as vice-president (1929–1934), secretary (1935–1939, 1942–1944), assistant secretary (1940–41), and adult supervisor of the youth council.

Dupuy ran branch campaigns fighting job discrimination against African Americans, reporting on police violence against African Americans, preparing African Americans to register to vote, and raising funds for the local and national NAACP. She was particularly passionate about anti-lynching cases. During 1936, Dupuy ran a campaign to defend Walter Ferguson, who was accused of murdering a white student. The branch raised $750 for the case and retained a white lawyer. While Ferguson was found guilty, the death penalty was avoided, which was unusual for the South in this period. Dupuy supervised the youth council of the local NAACP from her own home in the 1930s and early 1940s, and helped to conduct such citywide campaigns as the Buy Negro Campaign of 1938, to “create interest among Negroes towards patronizing racial enterprises.”

A major aspect of Dupuy’s work for the NAACP was in recruitment for the organization, and the Baton Rouge branch had 1,671 members by 1945. Many of these members, such as the businessman Horatio Thompson, played important roles in future civil rights action in the city and laid the foundation for the Baton Rouge bus boycott of 1953, which was the forerunner of the Montgomery bus boycott.