Louisiana Highway 21 | ||||
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Route information | ||||
Maintained by Louisiana DOTD | ||||
Length | 51.76 mi (83.30 km) | |||
Existed | 1955 renumbering – present | |||
Major junctions | ||||
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North end | ![]() | |||
Highway system | ||||
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Louisiana Highway 21 (LA 21) is a state highway in Louisiana that serves St. Tammany and Washington Parishes. It spans 51.76 miles (83.30 km) and is bannered north/south.
A state highway, state road, or state route is usually a road that is either numbered or maintained by a sub-national state or province. A road numbered by a state or province falls below numbered national highways in the hierarchy. Roads maintained by a state or province include both nationally numbered highways and un-numbered state highways. Depending on the state, "state highway" may be used for one meaning and "state road" or "state route" for the other.
Louisiana is a state in the Deep South region of the South Central United States. It is the 31st most extensive and the 25th most populous of the 50 United States. Louisiana is bordered by the state of Texas to the west, Arkansas to the north, Mississippi to the east, and the Gulf of Mexico to the south. A large part of its eastern boundary is demarcated by the Mississippi River. Louisiana is the only U.S. state with political subdivisions termed parishes, which are equivalent to counties. The state's capital is Baton Rouge, and its largest city is New Orleans.
From the south, LA 21 begins at an intersection with Louisiana Highway 22 and Louisiana Highway 1077 in Madisonville, where LA 21 assumes the trajectory of LA 1077 and heads northeast. LA 1077 branches to the northwest before LA 21 intersects Interstate 12. [1] From south of I-12 and until joining US 190 Business on 21st Avenue in Covington, LA 21 is multilane, in places divided by a median or by a center turn lane, with some control of access. [2]
Louisiana Highway 22 (LA 22) is a state highway located in southeastern Louisiana. It runs 71.15 miles (114.50 km) in a general east–west direction from the junction of LA 75 and LA 942 in Darrow to U.S. Highway 190 (US 190) in Mandeville.
Louisiana Highway 1077 (LA 1077) is a state highway located in southeastern Louisiana. It runs 20.61 miles (33.17 km) in a general north–south direction from a dead end at Lake Pontchartrain in Madisonville to a junction with LA 25 south of Folsom.
Interstate 12 (I-12) is an Interstate Highway located entirely within the U.S. state of Louisiana. It spans a total of 86.65 miles (139.45 km) in an east–west direction from I-10 in Baton Rouge to an interchange with both I-10 and I-59 in Slidell. Along the way, it passes through the city of Hammond, where it intersects I-55 and US 51. It also serves the smaller cities of Denham Springs and Ponchatoula, as well as the St. Tammany Parish cities of Covington and Mandeville. Skirting the northern shore of Lake Pontchartrain, I-12 serves as a northern bypass of the New Orleans metropolitan area and as an alternate route for I-10, which serves the city of New Orleans itself.
Through most of Covington LA 21 is in a mostly two-lane undivided concurrency with US 190 Business, which returns to U.S. Route 190 on the east side of Covington—an area known as Claiborne Hill. After intersecting US 190 and before leaving Covington cosigned as Military Road, LA 21 absorbs LA 36 and continues northeastward, absorbing LA 59 and entering a brief concurrency with Louisiana Highway 40 in Bush for less than one mile (1.6 km). Between Bush and Sun, LA 21 widens to a four lane, divided highway after merging Louisiana Highway 41, continuing due north from the merge. In Sun LA 21 absorbs LA 16 and continues northward to Bogalusa, where LA 21 intersects LA 10. LA 21 then runs north through Varnado and Angie before becoming Mississippi Highway 35 at the state line.
A business route in the United States is a short special route connected to a parent numbered highway at its beginning, then routed through the central business district of a nearby city or town, and finally reconnecting with the same parent numbered highway again at its end.
U.S. Route 190 (US 190) is an east–west United States Highway in Louisiana and Texas. Segments of US 190 will be upgraded to Interstate 14 (I-14), the first 24.8-mile (39.9 km) segment was opened on January 26, 2017.
A concurrency in a road network is an instance of one physical roadway bearing two or more different route numbers. When two roadways share the same right-of-way, it is sometimes called a common section or commons. Other terminology for a concurrency includes overlap, coincidence, duplex, triplex, multiplex, dual routing or triple routing.
![]() | This section contains a table that is missing mileposts for one or more junctions. |
Parish | Location | mi | km | Destinations | Notes |
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St. Tammany | Madisonville | ![]() ![]() | south end of LA 1077 overlap | ||
| ![]() ![]() | north end of LA 1077 overlap | |||
| ![]() | I-12 exit 59 | |||
Covington | ![]() ![]() ![]() ![]() | south end of US 190 Bus. overlap | |||
![]() ![]() | interchange | ||||
![]() ![]() ![]() ![]() ![]() ![]() | north end of US 190 Bus. overlap | ||||
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Waldheim | ![]() | south end of LA 1083 overlap | |||
![]() | north end of LA 1083 overlap | ||||
| ![]() | south end of LA 40 overlap | |||
| ![]() | north end of LA 40 overlap | |||
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Sun | ![]() | ||||
Washington | | ![]() | |||
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Bogalusa | ![]() | ||||
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Varnado | ![]() | ||||
Angie | ![]() | ||||
![]() | south end of LA 438 overlap | ||||
![]() | north end of LA 438 overlap | ||||
| ![]() | Mississippi state line | |||
1.000 mi = 1.609 km; 1.000 km = 0.621 mi |
U.S. Route 425 is a north–south United States highway, first commissioned in 1989. Its route number is a "violation" of the usual AASHTO numbering scheme, as it comes nowhere near its implied "parent", US 25.
U.S. Route 165 is a north–south United States highway spur of U.S. Highway 65. It currently runs for 412 miles (663 km) from U.S. Route 90 in Iowa, Louisiana north to U.S. Highway 70 in North Little Rock, Arkansas. The route passes through the states of Arkansas and Louisiana. It passes through the cities of Monroe and Alexandria in Louisiana. A segment of US 165 serves as a routing of the Great River Road within Arkansas.
Louisiana Highway 8 is a state highway in Louisiana. It spans 156 miles (251 km) beginning at the Louisiana/Texas state line west of Leesville and ending at an intersection with U.S. Route 425 and LA 15 in Sicily Island.
Louisiana Highway 28 (LA 28) is a state highway located in central Louisiana. It runs 86.97 miles (139.96 km) in an east–west direction from the junction of U.S. Highway 171 (US 171) and LA 8 in Leesville to US 84 west of Jonesville.
Louisiana Highway 6 (LA 6) is a state highway located in western central Louisiana. It runs 54.52 miles (87.74 km) in an east–west direction from the Texas state line southwest of Many to U.S. Highway 71 (US 71) and U.S. Highway 84 (US 84) in Clarence.
Louisiana Highway 12 (LA 12) is a state highway located in southwestern Louisiana. It runs 34.64 miles (55.75 km) in an east–west direction from the Texas state line west of Starks to a junction with U.S. Highway 171 (US 171) and U.S. Highway 190 (US 190) in Ragley.
Louisiana Highway 16 (LA 16) is a state highway located in southeastern Louisiana. It runs 110.27 miles (177.46 km) in a general east–west direction from LA 22 south of French Settlement to LA 21 in Sun.
Louisiana Highway 25 (LA 25) is a state highway located in southeastern Louisiana. 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.
Louisiana Highway 433 is a state highway in Louisiana that serves St. Tammany Parish. It spans 14.8 miles (23.8 km) in a west to east direction. It is known at various points as Thompson Road, Bayou Liberty Road, Pontchartrain Drive, Old Spanish Trail, and Rigolets Road.
Louisiana Highway 59 (LA 59) is a state highway located in St. Tammany Parish, Louisiana. It runs 11.74 miles (18.89 km) in a north–south direction from U.S. Highway 190 (US 190) in Mandeville to LA 21 north of Abita Springs.
Louisiana Highway 415 is a state highway in Louisiana. It spans north–south through West Baton Rouge Parish and Pointe Coupee Parish for 25.3 miles (40.7 km).
Louisiana Highway 112 is a state highway in Louisiana. It spans 80.9 miles (130.2 km) and runs from west to east. LA 112 is a mostly rural two lane highway with a maximum speed limit of 55 miles per hour (89 km/h) per hour. The western terminus is at an intersection with U.S. Route 171/U.S. Route 190 in Beauregard Parish and the eastern terminus at an intersection with US 167/US 71 in Rapides Parish. Although the highway runs west to east it meanders through three parishes and on the map appears to make a large S.
U.S. Highway 190 Business is a state highway in Louisiana that serves St. Tammany Parish. It spans 2.94 miles (4.73 km) in a southeast to northwest direction. It is known locally as 21st Avenue and Boston Street. It is also the route used to access LA 21 South.
Louisiana Highway 103 is a state highway located in St. Landry Parish that spans 39.5 miles (63.6 km) in a wide semi-circle around the north side of Opelousas. The route is not bannered but runs in an overall west–east direction from U.S. Highway 190 near Lawtell to LA 31 in Leonville. Along the way, it passes through the towns of Washington and Port Barre.
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