It runs 41.4 miles (66.6 km) in a west–east direction from LA 26 southeast of Oberlin to U.S. Highway 190 (US 190) in Opelousas.

[1] Along the way, it passes through the town of Mamou and intersects various north–south routes that service points along US 190 such as Elton, Basile, and Eunice.

LA 104 then heads in a general northeastern direction, zigzagging along section line roads, towards the town of Mamou.

The latter two highways connect with the modern alignment of LA 13 which skirts the western edge of town.

After another 1.3 miles (2.1 km), LA 104 curves to the northeast briefly before taking a southeastern course toward an area known as Point Blue.

[7][8][9] LA 104 was created with the 1955 Louisiana Highway renumbering, and its route has remained unchanged to the present day.