page_title: U.S. Route 20
section_title: Iowa
hierarchical_section_title: U.S. Route 20 / Route description / Iowa
caption_attribution_description: Photo taken from Gramercy Park in East Dubuque, the bridge is part of the U.S. Highway 20 route.
context_page_description: U.S. Route 20 or U.S. Highway 20 is an east–west United States highway that stretches from the Pacific Northwest all the way to New England. The "0" in its route number indicates that US 20 is a coast-to-coast route and major route. Spanning 3,365 miles, it is the longest road in the United States, and the route is roughly parallel to that of the newer Interstate 90, which is in turn the longest Interstate Highway in the U.S. There is a discontinuity in the official designation of US 20 through Yellowstone National Park, with unnumbered roads used to traverse the park.
  US 20 and US 30 break the general U.S. Route numbering rules in Oregon, since US 30 actually starts north of US 20 in Astoria, and runs parallel to the north throughout the state. The two run concurrently and continue in the correct positioning near Caldwell, Idaho. This is because US 20 was not a planned coast-to-coast route while US 30 was. US 20 originally ended at the eastern entrance of Yellowstone Park; it was extended in 1940.
  The highway's eastern terminus is in Boston, Massachusetts, at Kenmore Square, where it meets Route 2.
context_section_description: US 20 enters Iowa at Sioux City via the Missouri River crossing with I-129 and US 75. After skirting the southeast side of Sioux City as a freeway with US 75, US 20 continues east as an expressway to Moville. From Moville through north of Early at the junction with U.S. Route 71 and Iowa Highway 471, US 20 was reconstructed from a rural two-lane highway to a four-lane road. This segment re-opened October 19, 2018 and made it so that US 20 is a continuous four-lane highway for its entire length in Iowa. It passes to the north of Sac City, where it has another interchange with the realigned U.S. Route 71, then passes to the south of Fort Dodge and Webster City before intersecting I-35 near Williams.
  A new segment of freeway between US 65 south of Iowa Falls and Iowa Highway 14 opened in 2003 creating a continuous four-lane route from Moorland to Dubuque. The new segment shaved 16 miles (26 km) off US 20's length in Iowa. In the Waterloo/Cedar Falls area, the segment of US 20 overlapped by the Avenue of the Saints, which is also designated as Iowa Highway 27. US 20 passes Independence, Manchester, and Dyersville before reaching Dubuque. At Dubuque, US 20 crosses into Illinois over the Julien Dubuque Bridge.
caption: US 20 crosses the Mississippi River connecting Dubuque, Iowa, and East Dubuque, Illinois
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