# Louisiana Highway 21

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 signed north and south.

## Route description

From the south, LA 21 begins at an intersection with LA 22 and LA 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 (I-12). From south of I-12 and until joining U.S. Route 190 Business (US 190 Bus.) on 21st Avenue in Covington, LA 21 is multilaned, in places divided by a median or by a center turn lane, with some control of access.
Through most of Covington, LA 21 is in a mostly two-lane undivided highway concurrent with US 190 Bus., which returns to US 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.

## Major intersections

| Parish | Location | mi | km | Destinations | Notes |
| St. Tammany | Madisonville | 0.0 | 0.0 | LA 22 (Mulberry Street) / LA 1077 south (Main Street) – Fairview Riverside State Park, Maritime Museum | South end of LA 1077 overlap |
| St. Tammany | ​ | 1.2 | 1.9 | LA 1077 north to I-12 | North end of LA 1077 overlap |
| St. Tammany | ​ | 3.4– 3.6 | 5.5– 5.8 | I-12 – Hammond, Slidell | I-12 exit 59 |
| St. Tammany | Covington | 6.6 | 10.6 | US 190 Bus. west (West 21st Avenue) / North Tyler Street | South end of US 190 Bus. overlap |
| St. Tammany | Covington | 7.8 | 12.6 | US 190 east to I-12 – Mandeville, New Orleans | Interchange; westbound US 190 entrance only |
| St. Tammany | Covington | 7.9– 8.0 | 12.7– 12.9 | US 190 Bus. east to US 190 – Franklinton | North end of US 190 Bus. overlap |
| St. Tammany | ​ | 8.0– 8.1 | 12.9– 13.0 | LA 36 east (Covington Highway) – Abita Springs | Western terminus of LA 36 |
| St. Tammany | ​ | 11.9 | 19.2 | LA 1082 north (Old Military Road) | Southern terminus of LA 1082 |
| St. Tammany | ​ | 12.3 | 19.8 | LA 59 south (Range Line Road) – Abita Springs | Northern terminus of LA 59 |
| St. Tammany | ​ | 13.1 | 21.1 | LA 1084 east | Western terminus of LA 1084 |
| St. Tammany | Waldheim | 15.2 | 24.5 | LA 1083 south | South end of LA 1083 overlap |
| St. Tammany | Waldheim | 15.4 | 24.8 | LA 1083 north (Ben Williams Road) | North end of LA 1083 overlap |
| St. Tammany | ​ | 21.9 | 35.2 | LA 40 west / Daisy Road | South end of LA 40 overlap |
| St. Tammany | ​ | 22.4 | 36.0 | LA 40 east / Columbia Road | North end of LA 40 overlap |
| St. Tammany | ​ | 23.3 | 37.5 | LA 41 south – Slidell | Northern terminus of LA 41 |
| St. Tammany | Sun | 25.5 | 41.0 | LA 16 west | Eastern terminus of LA 16 |
| Washington | ​ | 27.4 | 44.1 | LA 1075 north | Southern terminus of LA 1075 |
| Washington | Bogalusa | 36.3 | 58.4 | LA 10 (Louisiana Avenue) | |
| Washington | ​ | 38.8 | 62.4 | LA 436 east | Terminus of LA 1082 |
| Washington | ​ | 42.9 | 69.0 | LA 436 – Pine, Franklinton | |
| Washington | Varnado | 44.0 | 70.8 | LA 436-1 east (Main Street) / Seal Cemetery Road – Varnado High School | Western terminus of LA 436-1 |
| Washington | Angie | 48.9 | 78.7 | LA 1071 east | Western terminus of LA 1071 |
| Washington | Angie | 49.4 | 79.5 | LA 438 west (Elm Street) | Eastern terminus of LA 438 |
| Washington | ​ | 52.1 | 83.8 | MS 35 north – Columbia | Mississippi state line |
| 1.000 mi = 1.609 km; 1.000 km = 0.621 mi Concurrency terminus Incomplete access ||||||