U.S. Highway 51 (US 51) is a part of the United States Numbered Highway System that spans from LaPlace, Louisiana to a point north of Hurley, Wisconsin. Within the state of Louisiana, the highway travels from the national southern terminus at US 61 in LaPlace to the Mississippi state line north of Kentwood.
After heading north through LaPlace to a junction with Interstate 10 (I-10) west of New Orleans, the highway joins I-55 on a twin-span viaduct across the Manchac Swamp. The bridge, which passes between Lakes Pontchartrain and Maurepas, is the second-longest bridge over water in the United States and serves as a vital hurricane evacuation route for the New Orleans metropolitan area.
With Ponchatoula served by the highway's only designated business route, US 51 splits from the interstate in the neighboring city of Hammond. For the remainder of its journey in southeastern Louisiana, the route closely parallels I-55, which carries the bulk of through traffic toward Jackson, Mississippi and points north. US 51 serves local traffic through a string of communities in Tangipahoa Parish situated along the Canadian National Railway line, including the towns of Independence, Amite City, and Kentwood.
Prior to 1951, US 51 began in downtown New Orleans and followed the route of US 61 to its current southern terminus in LaPlace. For a time in the late 1920s to mid-1930s, however, it was intended to follow a scenic route along the shore of Lake Pontchartrain known as the New Orleans–Hammond Lakeshore Highway. Construction difficulties and budget limitations led to the abandonment of the project before the portion through the swamps of St. Charles Parish could be completed.
Route description
LaPlace to Hammond From the south, US 51 begins at an intersection with US 61 (West Airline Highway) in Laplace, an unincorporated community located on the east bank of the Mississippi River in St. John the Baptist Parish. US 61 parallels the route of I-10 between New Orleans and Baton Rouge. US 51 heads northeast as an undivided four-lane highway with a center turning lane through a growing residential and commercial corridor. After , the route reaches the edge of town and passes through a diamond interchange with I-10 at exit 209. This interchange is also used to feed traffic between I-10 to the west and I-55 to the north as there is no direct connection. With a median replacing the center lane, US 51 proceeds a short distance to an intersection with Frenier Road, where signage directs through traffic to turn west and follow a ramp onto the elevated I-55 at exit 1. For the next , US 51 travels concurrently with the elevated four-lane interstate through the thickly wooded swamp lying between Lake Pontchartrain and Lake Maurepas. This twin-span concrete trestle is known as the Manchac Swamp Bridge and is the second-longest bridge over water in the United States. along the way, a tight diamond interchange at Ruddock connects with the grade-level pre-interstate alignment, which serves as a frontage road and closely parallels the entire stretch.
After , the highway elevates higher to cross Pass Manchac, a waterway that connects the two lakes and forms the boundary between St. John the Baptist Parish and Tangipahoa Parish. The area flanking the pass, generally called Manchac, contains a cluster of boat houses and fishing camps situated along the frontage road. This small community is also known as Galva on the south side and Akers on the north side. The highway proceeds through the swamps of southern Tangipahoa Parish for another before returning to grade. At this point, an exit primarily serving southbound traffic connects to the north end of the frontage road. Soon afterward, I-55/US 51 curves to the northwest at exit 23 while US 51 Bus. begins and splits off straight ahead into the small city of Ponchatoula. The interstate proceeds around the west side of town, an area of scattered suburban development within the thick pine forest. A cloverleaf interchange at exit 26 connects to LA 22, the primary east–west highway through Ponchatoula. US 51 departs from I-55 at the following exit and enters the neighboring city of Hammond, the largest city along its route.
Hammond to Mississippi state line Heading north on Morrison Boulevard, US 51 returns to its original capacity, an undivided four-lane highway with center turning lane. Almost immediately, the highway crosses over without intersecting I-12, a northern bypass of the New Orleans metropolitan area, just east of its interchange with I-55. For the remainder of its journey in Louisiana, US 51 parallels the route of I-55 at a distance generally between to the east. Passing to the west of the traditional downtown area, US 51 intersects US 190 (West Thomas Street), its main east–west commercial thoroughfare. This intersection also marks the northern terminus of US 51 Bus. Upon exiting Hammond, an intersection with LA 3234 (West University Avenue) connects the route with nearby Southeastern Louisiana University. Shortly afterward, US 51 narrows to an undivided two-lane highway and will remain in that capacity for the rest of its journey.
After passing through the community of Natalbany, US 51 enters the village of Tickfaw and begins to follow alongside the Canadian National Railway (CN) line. Both the highway and the rail line pass through a string of communities on the way to the Mississippi state line and intersect a series of rural east–west routes that often lead to nearby interchanges with I-55, the main route of through traffic in the area. In Tickfaw, this function is served by LA 442, which also has a brief concurrency with US 51 as the former makes a zigzag in the center of town. north of Tickfaw, US 51 passes through the town of Independence, where LA 40 connects to I-55 as well as points such as Loranger and Husser. Continuing due north for , US 51 enters Amite City, the parish seat. Initially traveling along 1st Street, one block distant from the railroad line, US 51 zigzags east onto Chestnut Street then north onto Central Avenue. One block later, flanked by the rail line and a row of antique brick storefronts, an intersection with LA 16 (Oak Street) in the center of town leads to I-55 and the towns of Franklinton and Montpelier.
Between two points known as Arcola and Fluker, located just north of the neighboring town of Roseland, US 51 has a concurrency with LA 10, another connection to Franklinton as well as Greensburg. US 51 proceeds through rural northern Tangipahoa Parish, passing through a village of the same name before entering Kentwood, the final town along its route. US 51 passes through Kentwood on 3rd Street and intersects LA 38, the main east–west thoroughfare, at Avenue G. The highway curves to the northeast on the way out of town and continues for another to the state line. During this stretch is the final junction with a state route, LA 1054, in an area known as Greenlaw. Immediately across the state line, US 51 continues into the Pike County, Mississippi town of Osyka en route to McComb.
Route classification and data The portions of US 51 not concurrent with I-55 are generally classified as an urban or rural major collector by the Louisiana Department of Transportation and Development (La DOTD). However, the section running through Hammond serves as an urban principal arterial. Daily traffic volume in 2013 peaked at 24,500 vehicles in Hammond, decreasing steadily to around 3,000 heading north toward Kentwood. After increasing to 14,700 through Kentwood, the figures dwindled to a low of 2,300 vehicles per day near the Mississippi state line. The posted speed limit is generally in rural areas, reduced to as low as through town. However, the multilane sections through LaPlace and Hammond carry a speed limit of .
The portion of US 51 utilizing the route of I-55 is classified as an urban interstate north of exit 23 and as a rural interstate otherwise. Daily traffic volume in 2013 averaged about 18,200 vehicles near I-10 and steadily increased to a peak of 31,200 vehicles between the Ponchatoula and Hammond exits. The posted speed limit is .
The entire I-55/US 51 frontage road (Old US 51) south of Ponchatoula is part of the Southern Swamps Byway in the state-designated system of tourist routes known as the Louisiana Scenic Byways. This byway also follows the route of LA 22 southwest from Ponchatoula through the Maurepas swamp to the town of Sorrento.
History US 51 was designated in November 1926 as one of the original routes of the numbered U.S. Highway system. It was the main traffic route connecting New Orleans to Jackson, Mississippi and Memphis, Tennessee in the days before the existence of the Interstate Highway System. The southern terminus of US 51 was originally located in downtown New Orleans at a junction with US 61 and US 90. Much of the distance between New Orleans and Hammond was intended to follow the New Orleans–Hammond Lakeshore Highway, an ambitious project by the Louisiana Highway Commission to construct a road through the LaBranche and Manchac swamps around the rim of Lake Pontchartrain. This proposed scenic highway was never fully realized, and US 51 effectively followed the route of US 61 through the New Orleans area until being truncated to its present terminus in LaPlace in 1951, eliminating the concurrency.
New Orleans–Hammond Highway
The New Orleans–Hammond Lakeshore Highway had been planned for several years when, in 1921, it was designated as part of State Route 33, one of the original 98 routes in the pre-1955 state highway system.
In New Orleans, Route 33 was designated to follow an existing road alongside a shipping canal from South Carrollton Avenue to an area on Lake Pontchartrain known as West End. (Much of this road still survives as Pontchartrain Boulevard and partly travels alongside the Pontchartrain Expressway, a section of I-10 that follows the old canal right-of-way.) However, the entire route along the lakeshore and on to Ponchatoula existed only on paper. North of Ponchatoula, the remainder of the route would have the benefit of following existing roads through the higher terrain there. The construction of the lakeshore highway was intended to provide a direct land connection between New Orleans and Hammond while taking advantage of the scenic beauty of Lake Pontchartrain and the surrounding swampland. In addition, the man-made embankment required to carry the road would serve as a levee to prevent lake water from inundating the extensive residential development envisioned to line the highway.
Construction Construction began in May 1923 to extend the highway south from Ponchatoula through the Manchac swamp to Frenier near the present intersection of I-10 and I-55. At the time, the method of road construction through such terrain involved the long and arduous task of dredging a canal along the intended right-of-way and piling up the spoils on the side of the canal to form an embankment. After a repeated process of machine-rolling and allowing for sufficient settling of the roadbed, the embankment would be surfaced with shells dredged from the lake. A timber bridge with a steel draw span was constructed across Pass Manchac, and smaller bridges totaling over spanned the numerous other waterways along the route. This link of the highway was officially opened on April 1, 1927 with a formal dedication following three weeks later. While still under construction, Route 33 was chosen as the official route of US 51 after the U.S. Highway system was implemented in November 1926.