South Dakota Highway 42

South Dakota Highway 42
State	SD
Type	SD
Route	42
Length mi	85.5
Established	1926
Direction a	West
Terminus a	Colman
Direction b	East
Terminus b	Iowa state line near Iowa Highway 9
Counties	Minnehaha County, Brookings County, Hanson County, Kingsbury County

South Dakota Highway 42 is an east–west state highway in eastern South Dakota connecting small towns, county seats, and regional corridors across Minnehaha County, Brookings County, Hanson County, and Kingsbury County. The route serves as a link between US routes and local arteries, providing access to agricultural areas near Sioux Falls, Brookings, Huron, and the Iowa border. It intersects federal highways and state routes, facilitating movement between communities such as Colman, Garretson, Dell Rapids, and Flandreau.

Route description

The western segment begins near Colman where the highway meets U.S. Route 81 and proceeds east toward Sioux Falls suburbs, intersecting county roads and crossing the Big Sioux River near Garretson. Continuing east, the corridor parallels rail lines owned by BNSF Railway and passes within proximity to Interstate 29 before turning toward Dell Rapids, where it intersects U.S. Route 77 and provides access to recreational sites at Paddy Creek Recreation Area and Palisades State Park. East of Dell Rapids, the route crosses expanses of farmland associated with South Dakota State University research plots, then enters Brookings County approaching Brookings area influence and intersects with I-29 connectors and county highways leading to Brookings Municipal Airport.

Further east, the highway traverses small towns such as Arlington and Hendricks-adjacent corridors (regional access only), intersects US 81 once again in places where alignments converge, and crosses tributaries feeding the Big Sioux River and James River basins. Approaching Kingsbury County, the roadway connects with secondary routes serving De Smet and rural townships, then reaches the Iowa state line where it transitions to Iowa Highway 9 toward Spirit Lake and Spencer.

History

Originally designated during the 1920s state highway numbering concurrent with the formation of the U.S. Route system, the corridor evolved from county roads and early auto trails such as segments associated with the Black Hills Trail and local feeder roads serving Milbank and Flandreau. Over decades, alignments were adjusted to accommodate the development of Interstate 29, improvements spurred by agricultural mechanization tied to institutions like South Dakota State University, and flood-control measures influenced by historical events including the 1930s Dust Bowl and later Flood of 1993 response efforts. During the mid-20th century, resurfacing and realignment projects funded through partnerships with the Federal Highway Administration and state agencies altered termini and produced bypasses around communities such as Dell Rapids and Garretson to improve safety near rail crossings operated by Union Pacific Railroad and BNSF Railway.

Notable upgrades in the late 20th and early 21st centuries included pavement rehabilitation concurrent with statewide programs referenced by the South Dakota Department of Transportation and federal funding mechanisms like the Intermodal Surface Transportation Efficiency Act of 1991 and the Transportation Equity Act for the 21st Century. Periodic bridge replacements have been undertaken in coordination with the United States Army Corps of Engineers when ties to regional water projects necessitated structural improvements.

Major intersections

The route intersects several major corridors and municipal access points, including connections with US 81, I-29 interchanges, and crossings of US 77 and state highways such as SD 115 and SD 19 in various segments. Key municipal junctions occur near Sioux Falls suburbs, Dell Rapids, Brookings-area connectors, and the Iowa border transition to Iowa 9. County-maintained crossroads provide access to airports like Sioux Falls Regional Airport and Brookings Municipal Airport, and to railheads served by BNSF Railway and Union Pacific Railroad.

Future and planned improvements

Planned projects identified by the South Dakota Department of Transportation and regional planning commissions include pavement overlays, shoulder widening to improve freight access tied to agricultural shipments to facilities such as grain elevators in Brookings and Sioux Falls, intersection safety enhancements near Dell Rapids and Garretson, and bridge rehabilitation funded through federal programs like the Fixing America’s Surface Transportation Act and state capital improvement plans endorsed by the South Dakota Legislature. Proposals have also considered multi-modal connections to transit services influenced by agencies including the Southeast Council of Governments and economic development initiatives tied to South Dakota Governor's Office priorities.

Related routes and spur connections

The highway links directly or indirectly with auxiliary routes and spurs such as county roads maintained by Minnehaha County and Brookings County governments, connector segments to US 81 and I-29, and transitional signage coordinating with Iowa Department of Transportation for continuity to Iowa 9. Nearby state highways including SD 19, SD 115, and SD 37 form a network facilitating regional mobility between communities such as Flandreau, De Smet, Arlington, and Colman.

Category:State highways in South Dakota