State Route 39

State Route 39
Type	State
Route	39

State Route 39 is a numbered highway serving as a regional connector across urban, suburban, and rural corridors. The route links multiple municipalities and intersects with several interstate and U.S. highways, providing freight, commuter, and recreational access. Its alignment traverses river valleys, mountain passes, and industrial districts, making it significant for regional planning agencies, transportation departments, and local municipalities.

Route description

The alignment begins near a lowland junction adjacent to Interstate 5, proceeding through an urban arterial that parallels the Great Northern Railway corridor and passes within blocks of downtown districts such as Union Station and City Hall Plaza. Moving eastward, the route crosses the Mississippi River basin, negotiates a series of grade-separated interchanges with U.S. Route 20 and U.S. Route 67, and skirts the edge of historic districts like Old Town and Market Square. In its midsection the highway climbs a mountain pass near the Appalachian Trail corridor, offering access to municipal parks administered by agencies such as the National Park Service and the U.S. Forest Service. Beyond the ridge the roadway descends into agricultural lowlands adjacent to Missouri River tributaries and intersects state routes that serve commuter suburbs like Springfield and Greenville.

The pavement varies from multi-lane divided highway within the metropolitan regions—where it is paralleled by local bus routes operated by Metropolitan Transit Authority and regional rail services like Amtrak—to two-lane rural segments under the jurisdiction of county road departments. Significant engineered features include a steel truss bridge over the Ohio River, a cut-and-cover tunnel beneath the Capitol Complex, and several roundabouts installed near historic town centers including Franklin and Yorktown. The corridor provides direct access to institutions such as State University, Regional Medical Center, and Convention Center.

History

The corridor has roots in early turnpike alignments established during the 19th century that connected trading posts referenced in the journals of explorers like Lewis and Clark Expedition and commerce hubs documented in Hudson's Bay Company records. During the early 20th century the alignment was formalized as part of a statewide numbered system influenced by planners from the American Association of State Highway Officials and civil engineers with ties to projects like the Lincoln Highway.

In the 1930s and 1940s the route saw major upgrades with Works Progress Administration projects that replaced timber bridges referenced in period records from the Federal Emergency Relief Administration and improved pavement funded through New Deal appropriations. Postwar growth spurred capacity expansions in the 1950s and 1960s, including interchange construction modeled after federal designs promulgated by the Bureau of Public Roads. Environmental reviews in the 1970s involved consultations with the Environmental Protection Agency and resulted in mitigation measures near wetlands listed by the Fish and Wildlife Service.

Recent decades have included corridor modernizations influenced by policy initiatives from the Department of Transportation and grants administered by the Federal Highway Administration, integrating Intelligent Transportation Systems technologies pioneered in pilot programs with universities such as Massachusetts Institute of Technology and University of California, Berkeley.

Major intersections

The route intersects several primary corridors that support interstate commerce and regional mobility: - Junction with Interstate 5 near the western terminus adjacent to freight yards associated with Union Pacific Railroad. - Interchange with U.S. Route 20 and U.S. Route 67 in the central business district near Convention Center. - Crossing over the Ohio River with a connection to Interstate 71 and Interstate 75 toward the east. - Connector ramps to State Highway 12 serving suburban communities and industrial parks linked to firms like General Motors and Boeing. - Access to regional airports including Regional Airport and proximity to air cargo facilities managed by Federal Aviation Administration.

Each major node has been the focus of capacity analyses using methodologies developed by the Transportation Research Board and traffic modeling tools from agencies such as Metropolitan Planning Organization.

Traffic and maintenance

Traffic volumes vary from peak urban counts measured by automatic traffic recorders maintained by the Department of Transportation to low rural Average Annual Daily Traffic figures monitored by county engineers. Freight movement along the corridor is significant, as documented in freight studies coordinated with the Federal Highway Administration and regional ports like the Port Authority. Roadway maintenance includes pavement preservation treatments specified by standards from the American Association of State Highway and Transportation Officials, bridge inspections following protocols of the National Bridge Inspection Program, and winter operations coordinated with state departments modeled after practices from State Emergency Management Agency.

Funding for operations and capital projects has been secured through mixes of state transportation revenue, federal grants administered by the Federal Transit Administration for multimodal elements, and bonds issued by regional transit authorities like Metropolitan Transit Authority.

Future developments

Planned improvements include corridor widening projects subject to environmental impact assessments prepared under the National Environmental Policy Act with stakeholder engagement involving municipal governments, advocacy groups such as American Automobile Association, and academic partners from State University. Proposals emphasize multimodal integration, adding bus rapid transit lanes linked to schemes by Transit Alliance, enhanced bicycle infrastructure inspired by designs from the League of American Bicyclists, and truck bypasses to relieve pressure on historic downtowns partnered with local chambers of commerce including Chamber of Commerce.

Technological upgrades consider deployment of connected vehicle infrastructure compatible with standards from the Institute of Electrical and Electronics Engineers and pilot autonomous freight corridors in collaboration with firms like Tesla and Waymo. Funding strategies contemplate federal infrastructure bills and discretionary grants overseen by the Office of the Secretary of Transportation.

Related routes

The corridor is paralleled and supplemented by several numbered highways, including regional state routes that provide alternate routing to suburbs served by Commuter Rail and local arterials feeding into Interstate 95 and U.S. Route 1. Auxiliary links include spur roads to industrial districts near Rail Yard and business loops serving historic centers like Main Street and Market Street.

Category:State highways