Louisiana Highway 21

Louisiana Highway 21
Route information
	Maintained by Louisiana DOTD
Length	51.76 mi (83.30 km)
Existed	1955 renumbering – present
Major junctions
South end	LA 22 / LA 1077 in Madisonville
	I-12 in Covington ; US 190 in Covington ; LA 36 in Covington; LA 59 south of Waldheim ; LA 40 south of Bush ; LA 41 in Bush; LA 16 in Sun ; LA 10 in Bogalusa
North end	MS 35 at state line
Highway system

Last updated April 20, 2019

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.

Route description

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.

Major intersections

Parish	Location	Destinations	Notes
St. Tammany	Madisonville	LA 22 (Mulberry Street) / LA 1077 south (Main Street) – Fairview Riverside State Park, Maritime Museum	south end of LA 1077 overlap
		LA 1077 north to I-12	north end of LA 1077 overlap
		I-12 – Hammond, Slidell	I-12 exit 59
	Covington	US 190 Bus. west (West 21st Avenue)	south end of US 190 Bus. overlap
		US 190 west to I-12 – Mandeville, New Orleans	interchange
		US 190 Bus. east to US 190 – Franklinton	north end of US 190 Bus. overlap
		LA 36 east – Abita Springs
		LA 1082 north
		LA 59 south – Abita Springs
		LA 1084 east
	Waldheim	LA 1083 south	south end of LA 1083 overlap
	Waldheim	LA 1083 north	north end of LA 1083 overlap
		LA 40 west	south end of LA 40 overlap
		LA 40 east	north end of LA 40 overlap
		LA 41 south
	Sun	LA 16 west
Washington		LA 1075 north
		LA 3124 north – Bogalusa Central Business District
	Bogalusa	LA 10
		LA 436 east
		LA 436 – Pine, Franklinton
	Varnado	LA 436-1 east
	Angie	LA 1071 east
		LA 438 west	south end of LA 438 overlap
		LA 438 east	north end of LA 438 overlap
		MS 35 north – Columbia	Mississippi state line
1.000 mi = 1.609 km; 1.000 km = 0.621 mi

Related Research Articles

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References

↑ LA 1077 has a separate interchange with I-12.
↑ As of 2010 much of the stretch between I-12 and 21st Avenue remained under reconstruction amid traffic jams.

External links

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[1] LA 1077 has a separate interchange with I-12.

[2] As of 2010 much of the stretch between I-12 and 21st Avenue remained under reconstruction amid traffic jams.