According to the United States Census Bureau, Mamou has a total area of 1.4 square miles (3.6 km2), all land.

[8] Within this vast stretch of prairie, the town site of Mamou was platted in 1907 by Curley C. Duson of Eunice.

He was president of the Mamou Town Site Company which opened an office on the corner of Seventh and Chestnut.

[8] As of the 2020 United States census, there were 2,936 people, 1,128 households, and 615 families residing in the town.

Mamou is also home of the world-famous Fred's Lounge, which features live Cajun music every Saturday morning.