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| Missouri Route 21 | |
|---|---|
| State | Missouri |
| Type | MO |
| Route | 21 |
| Length mi | ≈118 |
| Direction a | South |
| Terminus a | Bates County (near Crooked River) |
| Direction b | North |
| Terminus b | St. Louis County (near Herculaneum, Fenton) |
| Counties | Bates, Henry, St. Clair, Crawford, Phelps, St. Louis |
Missouri Route 21
Missouri Route 21 is a state highway in the U.S. state of Missouri that runs generally north–south across central and eastern portions of the state. The route connects rural Bates County areas with suburban and urban corridors near St. Louis County, intersecting major routes serving Kansas City, Springfield, and the Ozarks region. It serves both freight and commuter traffic, and provides access to recreational and historical sites including sections of the Mark Twain National Forest and riverfront communities along the Mississippi River.
Route 21 begins in southern Missouri near Butler County borders and proceeds north through a mixture of rural farmland in Bates and rolling hills of the Ozarks before entering more developed corridors approaching Jefferson County and St. Louis County. Along its alignment the highway intersects with state routes and U.S. highways such as U.S. Route 50, Interstate 44, and Interstate 55, and provides connections to the Missouri River and Meramec River. The corridor passes near communities including Potosi, De Soto, Festus, and Herculanum before terminating near suburban access points serving Fenton and Affton.
The roadway traces origins to early territorial roads used during westward expansion, serving trade and migration routes linked to Lewis and Clark Expedition era pathways and later 19th-century wagon trails that connected river ports like Ste. Genevieve and St. Louis. In the 1920s and 1930s Missouri established a numbered highway system that formalized alignments near Jefferson City and regional tracks between Springfield and St. Louis County. Throughout the 20th century the route was upgraded in segments to support increasing automobile use driven by national policies like the Federal Aid Road Act of 1916 and the Federal-Aid Highway Act of 1956, paralleling development trends seen along U.S. Route 66 and other Midwestern corridors. Flood events along the Mississippi River and storms affecting the Ozarks prompted resilient design projects similar to those on U.S. Route 63 and Interstate 44 corridors. Later improvements reflected suburban expansion tied to metropolitan growth of St. Louis and industrial traffic serving Anheuser-Busch distribution routes and regional logistics centers.
Major junctions include interchanges and crossings with several significant highways and local arterials. North–south and east–west connections occur at intersections with U.S. Route 50, U.S. Route 67, Interstate 44, and Interstate 55. The route also interfaces with state highways like Missouri Route 30, Missouri Route 47, and Missouri Route 221, and provides links to county roads serving Phelps and Crawford communities. These interchanges support access to regional hubs including St. Louis Lambert International Airport via connecting corridors and supply routes to manufacturing centers such as those in Jefferson County and St. Louis County.
Traffic volumes along the highway vary from low-density rural segments to high-demand suburban stretches approaching the St. Louis metro area and industrial nodes. Freight traffic includes trucks servicing distribution centers and raw-material shipments tied to regional industries such as Boeing suppliers and metallurgy plants near Herculaneum. Commuter flows increase during peak hours toward employment centers in St. Louis and satellite cities like Fenton and Festus. Seasonal tourism and recreational travel to destinations such as the Mark Twain National Forest, Meramec State Park, and riverfront events in St. Louis contribute to variable weekend and holiday demand patterns similar to those observed on corridors like Missouri Route 3 and U.S. Route 61.
Transportation planning agencies including the Missouri Department of Transportation and regional metropolitan planning organizations have evaluated capacity, safety, and resiliency upgrades for portions of the corridor. Proposed improvements have included lane additions, interchange reconstruction inspired by projects on I‑64 and I‑270, pavement rehabilitation, and stormwater mitigation measures modeled after flood-hardening efforts on U.S. 67. Funding discussions reference federal programs similar to the Infrastructure Investment and Jobs Act and state-level transportation priorities that influence sequencing of corridor projects. Local governments such as those in Jefferson County and St. Louis County coordinate land-use planning with transit and safety initiatives affecting bicycle and pedestrian accommodations near suburban nodes.
The highway provides access to numerous cultural, historical, and natural attractions. Travelers use it to reach outdoor destinations like Taum Sauk Mountain State Park, Hawn State Park, and sections of the Mark Twain National Forest as well as recreational waterways including stretches of the Meramec River and access points to the Mississippi River. Historic sites accessible from the corridor include early settlements such as Ste. Genevieve and mining heritage museums in Potosi, while arts and urban attractions in the St. Louis area—such as the Gateway Arch, Missouri History Museum, and performing arts venues affiliated with Washington University in St. Louis—are within driving distance. Local festivals in towns like Festus and De Soto drive seasonal visitation, complementing outdoor recreation and heritage tourism tied to the broader Ozarks region.
Category:State highways in Missouri