U.S. Route 18 in Iowa

U.S. Highway 18
Route information
Maintained by Iowa DOT
Length:	311.459 mi (501.245 km)
Existed:	November 11, 1926 – present
History:	Primary Road 19 from 1920–1926 National Parks Pike registered in 1920
Major junctions
West end:	US 18 near Canton, S.D.
	US 75 near Hull Iowa 60 at Sheldon US 71 at Spencer US 169 at Algona I-35 at Clear Lake US 218 at Charles City US 63 at New Hampton US 52 at Postville
East end:	US 18 / WIS 60 at McGregor
Location
Counties:	Lyon Sioux O'Brien Clay Palo Alto Kossuth Hancock Cerro Gordo Floyd Chickasaw Fayette Clayton Allamakee
Highway system
United States Numbered Highway System List Special Divided Replaced Iowa Primary Highway System Interstate U.S. State Secondary Scenic ← Iowa 17 US 20 →

U.S. Highway 18 (US 18) is the northernmost east–west U.S. Highway in the state of Iowa. As with all state highways in Iowa, it is maintained by the Iowa Department of Transportation (Iowa DOT). It enters the state by crossing the Big Sioux River between Inwood and Canton, South Dakota. It travels 311 miles (501 km) and connects Spencer, Mason City and Charles City. The highway leaves the state via the Marquette–Joliet Bridge over the Mississippi River at Marquette. Prior to becoming a U.S. Highway, the route US 18 follows was known as Primary Road No. 19 and the National Parks Pike.

US 18 begins at the Big Sioux River approximately 2 miles (3.2 km) east of Canton, South Dakota. It runs easterly through rural Lyon County, in the northwestern corner of the state. At Inwood it meets Iowa 182, which provides access to Sioux Falls, South Dakota, via Iowa 9 and South Dakota Highway 42. US 18 turns south at Inwood and heads into Sioux County. The highway crosses the Rock River on its way towards Rock Valley and Hull. West of Hull, at Perkins, US 18 juts to the south along US 75 before turning east again closer to Hull. The highway continues east towards Sheldon.

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Wikipedia