U.S. Highway 30 (US 30) is a major east–west U.S. Highway which spans 330 miles (530 km) across the state of Iowa. It is the longest primary highway in the state and is maintained by the Iowa Department of Transportation (Iowa DOT). The route in Iowa begins at the Missouri River crossing at Blair, Nebraska, and ends at the Mississippi River crossing at Clinton. Along the way, it serves Denison and Carroll in western Iowa, Boone, Ames, and Marshalltown in central Iowa, and Tama, Cedar Rapids, and DeWitt in eastern Iowa. Cutting across the central portion of the state, US 30 runs within close proximity of the Union Pacific Railroad's Overland Route for its entire length.
US 30 was originally conceived as a part of the Lincoln Highway, the first transcontinental highway in the United States. A route through Iowa was chosen because of the important link between Omaha, Nebraska, and Chicago, Illinois. As the U.S. Highway System came into being in the 1920s, and the Lincoln Highway became US 30, federal money started to pay for paving Iowa's dirt roads. By 1931, it had been paved across the entire state.
The route of the Lincoln Highway and US 30 has accommodated the changing needs of the traveling public. Early Lincoln Highway travelers were directed into many small towns as the route traveled 358 miles (576 km) across the state. Towards the middle of the 20th century, the route was straightened, bypassing most downtown areas and several towns altogether. More recently, long sections of US 30 have been upgraded to a four-lane expressway to meet the needs of increasing traffic. Since 2006, the highway has been designated an Iowa Heritage Byway by Iowa DOT, the first highway in the state with that distinction.
US 30 extends from west to east across the central portion of Iowa, with much of the highway traveling through rolling farmland. Small towns dot the entire route, which connects the larger cities of Denison, Ames, Cedar Rapids, and Clinton. Between Ogden and Mount Vernon, significant portions of the highway have been upgraded to a four-lane freeway.
US 30 enters the western end of Iowa by crossing the Missouri River on the Blair Bridge, located east of the Nebraska town of the same name. Adjacent to the highway bridge is the Union Pacific Railroad's river crossing for the Overland Route. The highway runs roughly parallel to the rail line for its entire run across Iowa. For nine miles (14 km), traffic moves through the flat Missouri River bottoms, passing DeSoto National Wildlife Refuge on the way to Missouri Valley. At Missouri Valley, it intersects Interstate 29 (I-29) at a partial cloverleaf interchange. It enters the Boyer River valley through the Loess Hills, a region of wind-deposited silt extending from north of Sioux City to extreme northwestern Missouri. The rolling Loess Hills rise 50–100 feet (15–30 m) above the roadway while the land in the valley stays relatively flat. US 30 enters Logan and intersects the eastern end of Iowa Highway 127 (Iowa 127). The highway runs parallel to the Boyer River as well as the Overland Route in a general northeast direction from Logan. Four miles (6.4 km) east of Logan is the western end of Iowa 44, which extends 105 miles (169 km) east to Des Moines.