It runs 38.72 miles (62.31 km) in a north–south direction from U.S. Highway 190 (US 190) in Covington to the Mississippi state line north of Warnerton.
The route extends from the Covington city limits through the rural hilly terrain beyond the New Orleans metropolitan area.
North of Franklinton, LA 25 crosses the state line and continues as Mississippi Highway 27 (MS 27) toward Tylertown.
At this intersection, US 190 turns southeast from Ronald Reagan Highway onto Collins Boulevard as it bypass the downtown area.
Over its first 10 miles (16 km), LA 25 makes a beeline toward the village of Folsom, running generally parallel and west of the Bogue Falaya River.
Signage directs motorists to nearby attractions along LA 40, including the Global Wildlife Center just inside neighboring Tangipahoa Parish.
The three routes then proceed concurrently across the Bogue Chitto River on the Chess Richardson Bridge, simultaneously entering the town of Franklinton.
After briefly curving along Washington Street into the downtown area, the three routes split in different directions at a four-way intersection.
[2][4][5] Curving to the northwest, LA 25 exits Franklinton, and the rural surroundings return as the highway parallels the east bank of the Bogue Chitto River for the remainder of its journey in Louisiana.
[2] The highway is classified as a rural minor arterial by the Louisiana Department of Transportation and Development (La DOTD).
In the original Louisiana Highway system in use prior to 1955, the modern LA 25 was part of State Route 34.
La 25—From a junction with La-US 190 at or near Chinchuba through or near Covington, Folsom and Franklinton to the Mississippi State Line near Warnerton.
[13] In 1958, the north–south portion of the Covington bypass was opened, which consisted of a new bridge across the Bogue Falaya River and the thoroughfare now known as Collins Boulevard.
[14][15] These improvements formed the northern end of the Greater New Orleans Expressway, of which the Lake Pontchartrain Causeway was the centerpiece.