This year marks the 100th anniversary of U.S. Highway 20, the longest highway in the United States that spans the continent through 12 states from the Atlantic to Pacific oceans. A portion of the highway’s 3,365 miles cross through Iowa from Dubuque to Sioux City. Collage by Iowa History Journal
March/April 2026 (Volume 18, Issue 2)
By Arvid Huisman
One of Iowa’s busier and more vital highways is celebrating its 100th birthday this year. Spanning the state from Dubuque to Sioux City, a rudimentary trail of gravel roads officially became U.S. Highway 20 in 1926.
Today the 302-mile four-lane route connects some 35 northern Iowa communities, creates an efficient, high-capacity corridor for truck and automobile traffic and fosters economic development.
Prior to 1926
The basic route now known as U.S. 20, dating back to before 1910, was a collaboration of unpaved roads that went through countless towns and villages and included 90-degree turns every few miles. In those days roads were often identified by names (rather than by numbers) and early-on this route was known as the Dragged Highway.
The name came from the method used to improve dirt roads. A road drag—often little more than a log or blade—was dragged by horses to improve the surface of a road.
In 1910 the Waterloo Reporter newspaper campaigned for a border-to-border road across northern Iowa. The same year four Sioux City men, including the president of the Sioux City Automobile Club, traveled across the state on a route proposed by the Sioux City Tribune. The trip took two full days, leaving early on a Monday morning and arriving in Dubuque on Tuesday evening.
The Waterloo Reporter’s campaign led to an organization created to advance and promote the road which ran generally parallel to the Illinois Central railroad line which at that time was the most efficient mode of travel across the state.
Named trails and routes
The Hawkeye Highway Association registered this route as the Hawkeye Highway in 1917. In the early 1920s, the State of Iowa designated Primary Highway numbers for the road. The portion from Sioux City to Fort Dodge was Primary No. 23 and from Fort Dodge to Dubuque was Primary No. 5.
Other named roads and automobile trail names overlapped portions of the Hawkeye Highway. These included the Grant Highway which stretched from Chicago west through northern Illinois across northern Iowa. Other named portions of the route included the Rainbow Trail and the Custer Battlefield Trail which ultimately extended beyond the Hawkeye Highway to other points.
After the state established Iowa Highway 23 from Sioux City to Fort Dodge via Cherokee, a portion of the Hawkeye Highway became known as the Hawkeye Cutoff or Hawkeye Short Cut because it provided a more direct route from Sioux City to Fort Dodge.
The Julien Dubuque Bridge crosses the Mississippi River in Dubuque and serves as the eastern gateway to northeast Iowa along U.S. Highway 20. Photo courtesy of Wikimedia Commons
By 1926 there were 718,013 registered motor vehicles in Iowa and automobile traffic was rapidly increasing. The named roads served their purpose in Iowa but when motorists drove to other states the road names sometimes ended, creating confusion as drivers motored on.
In Nebraska, the original U.S. 20 involved the Gordon Trail and other names. In Illinois the route was known as the Atlantic Yellowstone & Pacific (AYP) Highway and the Grant Highway.
In the mid-1920s the problem of interstate routes having inconsistent names was addressed by the American Association of State Highway Officials (AASHO.) That organization’s Joint Board on Interstate Highways proposed an interstate highway numbering plan in 1925. The initial U.S. Numbered Highway System was approved on Oct. 26, 1926.
It was this plan that designated the route from Dubuque to Sioux City as U.S. Highway 20. Nationally, U.S. 20 ran from Boston, Mass, to Yellowstone National Park in northwest Wyoming. It was later extended to Newport, Ore., making it the longest U.S. highway in the nation.
U.S. 20 in Iowa
U.S. 20 entered Iowa from Illinois over the Mississippi River on the High Bridge (also known as the Wagon Bridge.) Built in 1887, this structure was replaced with the 5,760-foot Julien Dubuque Bridge which opened in 1943 and continues to serve as the eastern gateway to northeast Iowa.
On the other side of the state U.S. 20 entered Iowa from Nebraska over the Missouri River on Sioux City’s Combination Bridge. In 1976 the Sergeant Floyd Bridge was constructed over the Missouri River 3.5 miles southeast of downtown Sioux City and in 1980 U.S. 20 was routed from Nebraska over the new bridge to a new four-lane bypass around the east side of Sioux City. Combination Bridge was replaced in 1981 by the new Siouxland Veterans Memorial Bridge.
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