In 1937, US 90 was relocated onto a new route bypassing Slidell and Pearl River, significantly reducing the distance between New Orleans and the Mississippi Gulf Coast.

It heads north along Ridgeway Boulevard as an undivided two-lane highway and travels through an area of marshland known as Irish Bayou.

The center lane disappears, and the two highways run concurrent for a short distance until reaching an intersection with Front Street.

Here, US 11 turns back to the northeast alongside the NS tracks while LA 433 continues straight ahead across the rail line onto Bayou Liberty Road.

Proceeding north for one mile (1.6 km), US 11 reaches the northern limit of Slidell and enters a partial cloverleaf interchange with I-12 at exit 83, briefly widening to a divided four-lane highway.

[4][6] Returning to two-lane capacity, US 11 continues north through the small suburb of Alton and intersects LA 1091 (Robert Boulevard), entering the town of Pearl River.

From this intersection, LA 3081 continues north along Main Street while US 11 turns southeast onto Concord Boulevard and crosses the NS line at grade.

Just north of the bridge is exit 5B, an interchange with a local road known as Old US 11, part of the pre-Interstate alignment that now serves Pearl River Wildlife Management Area.

[7] The annual average daily traffic (AADT) in 2016 ranged between about 18,900 vehicles near downtown Slidell and 3,250 in Irish Bayou, south of the Maestri Bridge.

[e][10][12] In December 1935, the current route of US 90 running directly between the Fort Pike Bridge and Pearlington was opened, shortening the distance from New Orleans to the Mississippi Gulf Coast by 22 miles (35 km).

[11] From the original southern terminus at Santa Rosa, US 11 then followed what is known as Old US 11, now a largely abandoned local road, to the state line where it crossed a now-demolished bridge over the Pearl River.

It then continued onto Old US 11 in Louisiana, locally maintained today as part of Pearl River Wildlife Management Area, to the site of the interchange with I-59 and the current route of US 11.

[17] Maps from 1939 indicate that US 11 briefly continued along the former route of US 90, turning southeast onto LA 433 to an intersection with current US 90 at the Fort Pike Bridge.

[17] Including the concurrency with US 90 into Downtown New Orleans, this routing would have represented the longest expanse of US 11 in Louisiana, totaling 51.8 miles (83.4 km).

[20] In December 1938, the state of Louisiana purchased the Pontchartrain Bridge at auction,[i] eliminated the tolls, and renamed it after New Orleans's mayor, Robert Maestri.

[29][30] The move was unpopular with the St. Tammany Parish police jury and with residents of Pearl River who would now have to travel several miles out of their way to reach Picayune, Mississippi.

[32] After further protests, the state made temporary repairs to the bridge to serve local traffic until an additional interchange was constructed to better connect the town with northbound I-59.

As the northern terminus of the highway has always been located at the Canadian border at Rouses Point, New York, US 11 would have been part of an international route connecting three countries.

The proposed route through southwestern Louisiana was to be part of a revival and extension of an early auto trail known as the Hug the Coast Highway.

Louisiana made several improvements to its part of the route, most notably a high-level bridge across the Gulf Intracoastal Waterway in Vermilion Parish.

[4][40] DOTD is currently engaged in a program that aims to transfer about 5,000 miles (8,000 km) of state-owned roadways to local governments over the next several years.

[41] Under this plan of "right-sizing" the state highway system, the portion of US 11 between US 190 (Gause Boulevard) in Slidell and LA 41 in Pearl River is proposed for deletion as it no longer meet a significant interurban travel function.