It runs 33.93 miles (54.61 km) in a north–south direction from U.S. Highway 61 (US 61) in Baton Rouge to the Mississippi state line north of Norwood.

The route connects a string of communities projecting northward out of Baton Rouge, the state capital, including the small suburban cities of Baker and Zachary.

The highway also intersects LA 10, an east–west cross-state route that connects with Jackson and Clinton, two nearby small towns of historic character.

LA 19 laterals off of US 61 as it heads north on Scotland Avenue alongside the Canadian National Railway (CN) tracks through an area within the Baton Rouge city limits known as Scotlandville.

Immediately after passing the local high school, LA 19 proceeds through a half diamond interchange with southbound I-110, which leads back to the downtown area.

Just north of the interstate, the suburban surroundings abruptly change as LA 19 passes a series of small industrial facilities, including an ExxonMobil chemical plant.

Widening to accommodate a center turning lane, LA 19 proceeds through Baker on Main Street, its principal commercial thoroughfare.

North of Baker, LA 19 passes through the small city of Zachary, where it diverges slightly from the CN railroad line for the first time.

The highway intersects LA 64 (Main Street) in the center of town, connecting with US 61 to the west and the city of Central to the east.

Once the highway crosses into rural East Feliciana Parish at Slaughter, the figure drops off sharply, reaching an estimate of 2,200 vehicles toward the Mississippi state line.

[6][11] The remainder of present-day LA 19, consisting of the southern portion of the route between Scotlandville and Slaughter, was added to the state highway system in 1928.

[7][13] This improvement eliminated two grade crossings of the Illinois Central (now the Gloster Southern) railroad tracks and streamlined the route through Zachary.

The section between LA 423 and Baker was widened in the late 1970s[18][19] and extended south to connect with the newly constructed extension of I-110 around 1982.