Its history is rooted in its waterways and its large expanse of fertile soils ideal for farming.

[4] As of the 2020 United States census, there were 21,039 people, 8,552 households, and 5,484 families residing in the parish.

During the "Solid South" era, conflicts over trade policy often caused Assumption Parish to deviate somewhat from overwhelming Democratic support, as did rebellion in the Acadiana region against Woodrow Wilson's perceived hostility towards France.

[12] Since the Dixiecrat revolt, by contrast, Assumption has been a typical rural South Louisiana parish in its political behaviour.

With the nomination of the more centrist Southerner Jimmy Carter in 1976, Assumption became again Democratic leaning until the 2000s, when, like all of the rural white South, it has turned powerfully Republican.