In the late 1800s, part of the former plantation was used as an experimental farm operated by Southern University and A&M College.

[6] Non-agricultural development began in 1894, when the Illinois Central Railroad (now Canadian National) built a repair yard and roundhouse adjacent to the current city hall.

[7] Prior to the Huey P. Long Bridge being built, Harahan was one of few points on the entire Mississippi River where railcars could cross.

The three largest barges in the world, the Mastodon, the Mammoth and El Grande once called Harahan home.

By 1910, Wedell-Williams on the eastern edge of Harahan, had become the de facto New Orleans airport,[8] and aviation pioneer John Moisant died there in a plane accident while preparing for a competition.

In 1930, the Huey P. Long Bridge was opened, increasing the importance of Harahan and by 1940, the population had risen to 1,082 citizens.

[11] During World War II, Camp Plauche was established on the current land occupied by Elmwood.

[12] In addition to the camp, Freiburg Mahogany manufacturing began producing critical aircraft and boat components for the war effort.

This activity spurred economic growth, particularly new homes; Harahan's population tripled during this period.

Numerous improvements were undertaken, including modernizing the police and fire departments, paving more streets and building a water treatment facility.

Completion of Earhart Expressway, making access to New Orleans proper much easier, influenced this growth as the appeal of Harahan as a “bedroom community.” Today, Harahan is directly influenced by its relationship with the larger surrounding areas including Jefferson Parish and the city of New Orleans.

Against nationwide demographic trends since 2020,[19] Harahan has remained predominantly non-Hispanic white as non-White Americans migrate to other suburban communities surrounding New Orleans.