The route connects the town of Livonia with New Roads, the parish seat, and other points along the False River via LA 1.

US 190 connects to Baton Rouge on the east and Opelousas on the west, while LA 411 heads southward along Bayou Grosse Tete toward Maringouin.

From this intersection, LA 78 turns to the northwest and quickly begins a long curve back to the northeast through an area of mixed rural and residential development.

4.3 miles (6.9 km) later, the route reaches its end at LA 1 in Parlange, located on the west bank of the False River.

30, approximately six miles southwest of New Roads, Pointe Coupee Parish, thence proceeding in a westerly direction to its intersection with State Highway Route No.

[9][10] In 1933, a new highway was constructed along the New Orleans, Texas and Mexico Railway (now the Union Pacific Railroad) through Livonia, essentially replacing Route 7 between Baton Rouge and Krotz Springs.

[13][14] Sometime before the 1955 Louisiana Highway renumbering, Route 136 was re-routed to begin at US 190 (the southern terminus of the present LA 78) and proceed north through Livonia.