Google Street View Timelapse - LA-25 N - Bogue Chitto State Park to Mississippi State Line

Pre-1955 route designation
In the original Louisiana Highway system in use prior to 1955, the modern LA 25 was part of State Route 34.[8] Designated in 1921 as one of the original 98 state highways, Route 34 also followed the present US 190 corridor from Covington to Slidell.[8][9] US 190 was assigned to this portion of the route in 1926 when the U.S. Highway System was created.[10][11] The two highways remained co-signed on the shared route until this practice was largely abandoned with the 1955 Louisiana Highway renumbering.[8]

Initial routing and subsequent truncations
LA 25 was created in the 1955 renumbering, replacing the portion of former Route 34 independent of US 190.

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.[12]

— 1955 legislative route description[12]
During its first year, LA 25 extended south of Covington to a terminus at what is now LA 22 in Mandeville since the renumbering occurred when US 190 was temporarily routed through Madisonville and Ponchatoula.[8] The exact southern terminus of LA 25 was at the present intersection of US 190 and LA 3228 (Asbury Drive). At that time, the highway between Mandeville and Covington was a two-lane road without interchanges or control of access. The original roadbed followed the current southbound lanes south of I-12 and the northbound lanes north of I-12. Additionally, the US 190 bypass of Covington did not yet exist. The original route through town followed the present US 190 Bus. north to LA 21, turning west onto Boston Street then north onto Columbia Street to the present southern terminus of LA 25. When US 190 was moved back to its regular route through Covington in 1956, the southern terminus of LA 25 was cut back to the intersection of Boston and Columbia Streets.[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. LA 25 was initially moved onto the bypass, which took it out of Downtown Covington. (The old route along Columbia Street became part of an extended LA 437 and the newly designated LA 437 Spur until being removed from the state highway system in 2015.)[1][16] In 1969, the Covington bypass was completed, which consisted of the east–west portion now known as Ronald Reagan Highway. Now connecting to US 190 at either end, that route was moved onto the bypass, with the old route through the downtown area becoming US 190 Bus., and LA 25 was cut back once more to its present southern terminus.[17]

Later improvements