Length in Iowa: 301 miles/484 kilometers
Western terminus: Nebraska state line (Missouri River)
at Sioux City, with I-129 and US 75
Eastern terminus: Illinois state line
(Mississippi River) at Dubuque
Entrance photos
Counties: Woodbury, Ida, Sac, Calhoun, Webster, Hamilton, Hardin,
Grundy, Black Hawk, Buchanan, Delaware, Dubuque
Cities along route: Sioux City, Lawton, Moville, Correctionville, Holstein, Early, Knierim, Moorland, Fort Dodge (via Business US 20),
Webster City, Owasa, Dike, Hudson, Cedar Falls, Waterloo, Evansdale, Elk Run Heights, Raymond, Jesup, Independence, Winthrop, Manchester, Delaware, Earlville, Dyersville, Farley, Epworth, Peosta, Dubuque
NHS: Entire route
Commercial and Industrial Network: Entire route
Freeway segments:
4½ miles, from Nebraska state line to Business US 20, east and
south of Sioux City
132 miles, from IA 17 near Webster City to IA 38 at Delaware
Expressway segments:
124 miles, from the split with US 75 outside of Sioux City to IA 17 near Webster City. (A less-than-one mile segment through Lawton is currently two lanes with a wide painted median; it was four lanes undivided in the past. It also becomes a five-lane highway for one mile through Correctionville.) Interchanges are located at US 71 north/IA 471, US 71 south/County Road N14, IA 4, Business US 20/County Road D36 (signed as D20), US 169, and Business US 20/County Road P59 southeast of Fort Dodge.
38 miles, from IA 38 in Delaware to Locust Street in Dubuque; includes interchanges at Earlville, Dyersville (2), Farley, Epworth, and Peosta, plus two in Dubuque after a series of traffic signals.
Exit lists:
Sioux City bypass
Segment from US 71 to I-35
Segment from I-35 to I-380
Segment from I-380 to US 61
Multiplexes:
4½ miles with US 75, from the Nebraska state line to
the Gordon Drive interchange east of Sioux City; this includes a quarter-mile with
I-129 from the state line to I-29.
¼ mile with IA 31 in Correctionville
1½ miles with US 59 east of Holstein
10 miles with US 71 between Exit #71 near Early and Exit #82 northeast of Sac City
4½ miles with IA 17 west of Webster City
1 mile with IA 58 on the south edge of Cedar Falls
13 miles with IA 27, between IA 58 in Cedar Falls and the
split with I-380 east of Raymond; this includes a 6-mile triplex with I-380 east of Waterloo.
20 miles with US 52, between IA 136 in Dyersville and the Southwest Arterial/Seippel Road in Dubuque
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Designated: October 16, 1926, replacing IA 34 across the Combination Bridge in Sioux City, IA 23 (I) (the Hawkeye Cutoff) between Sioux City and Fort Dodge, and IA 5 (I) (the Hawkeye Highway) from Fort Dodge to Dubuque into Illinois (except for the segment between Cedar Falls and Waterloo, where it replaced IA 40 (I)).
Paving history: At the time of designation, the segments through Woodbury County and from the Grundy/Black Hawk county line west of Cedar Falls to Winthrop (excluding a short segment west of Winthrop at a railroad crossing) were paved.
1927: Paved from Dyersville to Epworth
1928: Paved from Winthrop to Dyersville, and from Epworth to Dubuque
1929: Paved from Fort Dodge to Webster City and from the Black Hawk/Grundy county line to the Butler/Grundy County line east of Ackley, while the gap west of Winthrop was paved.
1930: Paved from the Calhoun/Webster county line to IA 16 (later US 169) in Fort Dodge (on a new diagonal alignment in western Webster County), from Webster City to Williams, and from Iowa Falls to the Butler/Grundy county line (on a new alignment)
1932: Paved from Cushing to Holstein and from Williams to Alden (on a new alignment)
1933: Paved through Fort Dodge (on a segment shared with US 169 at the time) and from Alden to Iowa Falls
1934: Paved from Early to Sac City and Rockwell City to Calhoun/Webster county line
1935: Paved from Holstein to a point southeast of Schaller (on a new alignment that was approved June 25, creating IA 328 to serve Galva and extending IA 110 along a former piece of US 20 south of Schaller)
1937: Paved from Sac City to Lytton
1938: Last unpaved segments, from a point southeast of Schaller to Early (on a new alignment) and from Lytton to Rockwell City (on a new diagonal alignment east of Lytton), paved
Major alignment changes:
August 31, 1943: Julien Dubuque Bridge opens between Dubuque and East Dubuque, IL. (The Highway Commission moved US 20 from Locust Street to Dodge Street on January 24, 1940, in anticipation of the bridge.)
November 24, 1954: Straightened between Sioux City and Moville; the old segment of US 20 west of there followed Correctionville Road and 180th Street.
September 19, 1958: Realigned between Waterloo and Jesup along a new road east of Waterloo, now known as Dubuque Road. An extension of IA 281 replaced part of the old segment that followed Independence Avenue in Waterloo.
October 19, 1958: Straightened between Moville and a point east of Cushing, creating IA 403 (I) as a spur into Cushing. The old segment is now County Road D22.
August 31, 1959: Realigned between IA 136 near Dyersville and Dubuque; it previously followed what is now Old Highway Road in Dubuque County. The old segment was redesignated as IA 416 on October 21.
December 13, 1964: Realigned between IA 38 near Delaware and IA 136; the old segment, which had been unsigned IA 947 between 1964 and 1980, is now County Road D22.
For alignment changes in Sioux City, Fort Dodge, Waterloo/Cedar Falls, and Dubuque that are not listed here, please see their respective highway chronology pages.
Upgrades:
October 19, 1958: Expressway segment east of Moville opened
August 31, 1959: 3-mile expressway segment southwest of IA 416 (now Old Highway Road) west of Dubuque opened, adding to an existing four-lane segment between there and Grandview Avenue in Dubuque.
August 25, 1964: 2½-mile expressway segment near Holstein opened
November 16, 1964: Expressway segment between Sioux City and Moville opened. The 2½-mile expressway segment near Holstein, which will eventually connect with the other expressway segments, also opened in 1964.
December 11, 1968: First piece of freeway, 3 miles between US 69 near Blairsburg and I-35, completed. The 1969 state highway map and some commercially-produced maps in the early 1970s marked this as IA 520 — the working number for the whole proposed cross-state freeway during this era was "Freeway 520" — but I am not sure if the road was signed as such. Legal descriptions referred to the freeway segment in Hamilton County as IA 520 until May 12, 1981.
November 15, 1974: 16-mile freeway segment from IA 187 in eastern Buchanan County to IA 38 at Delaware opened. (The 9-mile segment from IA 187 to IA 13 near Manchester was completed in 1971 as IA 520, but US 20 traffic was not rerouted until this time.)
June 28, 1976: 9-mile freeway segments from IA 17 at Webster City to US 69 completed.
November 22, 1976: Freeway segment from the Nebraska state line to I-29 opened (it was signed exclusively as I-129 at first)
December 10, 1976: Freeway segment from I-29 to Lakeport Street opened; this piece was initially designated as IA 520, as US 20 traffic was not rerouted right away.
June 29, 1979: Remainder of the freeway in the Sioux City area finished; old segment became an extended IA 12 (until 2000) and Business US 20.
July 20, 1979: 12-mile freeway segment from IA 150 at Independence to IA 187 opened
October 20, 1979: 4½-mile freeway segment between the west junction of IA 17 and Webster City opened; this created the multiplex with IA 17.
May 12, 1981: Relocated onto I-35 between exits #142 and #147, following the designation of IA 928 along the old segments in Hamilton County east of IA 17; it also took over a piece of former County Road D20 east of I-35 that the state took control of on July 23, 1980. (State transportation maps during the 1980s, however, did not show any changes to US 20.)
August 26, 1983: 16-mile freeway segment between IA 297 near Raymond and IA 150 at
Independence opened; the old segment became IA 939. (Before that, a short two-lane segment between the former IA 248 and IA 150 was built in 1981 as a bypass of Independence for truck traffic. Traffic then used the former IA 248 to reach US 20.)
August 9, 1984: 7-mile freeway segment between IA 21 in Waterloo and IA 297 opened
December 7, 1984: 3-mile freeway segment between US 63 and IA 21 in Waterloo opened. (Neither of the two previous segments were signed as US 20 at first, but were designated by the state as IA 520.)
June 14, 1986: 7-mile freeway segment from the Black Hawk/Grundy county line
to US 63 opened; US 20 then replaced IA 57 between the county line and IA 14, sharing 9 miles with IA 14 into Parkersburg, with IA 57 replacing the old US 20 between Parkersburg and Cedar Falls.
July 2, 1987: 11-mile expressway segment from Webster County Road P59 to IA 17 completed
November 29, 1987: 11-mile expressway segment from IA 38 to the Delaware/Dubuque county line west of Dyersville opened
May 24, 1988: 1-mile expressway segment through Dyersville (including the interchange with IA 136) opened
June 7, 1988: 6-mile expressway segment through Peosta to the previous end of the four-lane west of Dubuque opened
November 17, 1988: 4-mile expressway segment through Epworth (including the interchange) opened
November 22, 1988: 8-mile expressway segment, from Dyersville to the end of the Epworth segment (including the interchange at Farley) opened, completing the four-lane link between Waterloo and Dubuque
December 7, 1990: 3-mile expressway segment between US 169 south of Fort Dodge and County Road P59 completed; most of the old route became Business US 20. A new 5-mile segment from Moorland to US 169 opened to two lanes at the same time.
October 7, 1991: 15-mile freeway segment between I-35 and US 65 in Hardin County opened, dropping the concurrency with I-35; 13 of those 15 miles were originally two lanes. From the east end of the freeway US 20 multiplexed with US 65 for five miles south of Iowa Falls, adding to the additional six-mile multiplex north and east of there. The old segment became unsigned IA 941.
November 7, 1996: Improvements to Dodge Street in Dubuque, which include interchanges
at Grandview Avenue and Bryant Street, finished.
July 14, 2000: Former two-lane freeway between County Road R77 and US 65 widened to four lanesNovember 15, 2000: 12-mile freeway segment between IA 14 and the Grundy/Black Hawk county line opened; the old segment was unsigned IA 263 (II) until it was turned over in early 2003.
August 22, 2003: 27-mile freeway segment between US 65 and IA 14 opened, completing the four-lane link between Fort Dodge and Dubuque and dropping the multiplexes with the abovementioned highways. The old segment became an extension of IA 57, removing US 20 from Franklin and Butler counties.
July 18, 2005: 5-mile expressway segment from a point east of Moorland to US 169 opened
December 15, 2010: 21-mile expressway segment from IA 4 in Calhoun County to the end of the existing segment near Moorland opened. The old segment from Rockwell City to Moorland is now County Road D36, while US 20 was temporarily multiplexed with IA 4 for 3½ miles south of this interchange.
November 19, 2012: 26-mile expressway segment between US 71 near Early and IA 4 opened; the old US 20 segment through Sac City and Lytton became an extension of County Road D36.
November 2015: 1-mile segment through Correctionville expanded from two to five lanes; this will connect with future expressway segments.
November 22, 2017: 3½-mile expressway segment between County Road L25 and the western split with IA 31 in Correctionville opens
September 17, 2018: 7½-mile expressway segment between County Road D22 and County Road L25 opens, closing the gap between Moville and Correctionville.
October 4, 2018: 17-mile expressway segment between US 59 and US 71 opens
October 17, 2018: 11-mile expressway segment between Correctionville and US 59 opens, completing the four-lane segment between Sioux City and Dubuque.
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Sioux City: Designated along 7 miles of US 20's old alignment after the freeway bypass opened in 1979. It is one of the few business routes to straddle two states, even though signage is sparse in Nebraska. The route follows Dakota Avenue from I-129 northward through South Sioux City, NE. Then it joins US 77 across the Missouri into Iowa, I-29 for a short distance, and Gordon Drive eastward from downtown Sioux City to US 20. The segment of Gordon Drive from the I-29 split to US 20/75 was co-signed with IA 12 until sometime in 2000 and retains the IA 12 designation. On July 1, 2012, the state took over jurisdiction of a short piece of Virginia Street and moved the IA 12 designation there, as eastbound Business US 20 traffic has to use this segment to access Gordon Drive after I-29 was reconstructed; the segment of Gordon Drive between Pearl and Virginia Streets, which merges into the I-29/US 77 interchange heading west, now carries the IA 812 designation. The entire segment through Iowa is part of the NHS. (Terminus photos)
Fort Dodge: Designated in 1990 along 13 miles of US 20's old
alignment after the expressway bypass opened, and approved by AASHTO on April 21, 1996. The route enters via County Road D20, follows Kenyon Road and 5th Avenue South in Fort Dodge before turning southward along County Road P59 east of town to connect with US
20. Most of the route, except for the two-mile duplex with Business
US 169 (which is actually IA 926), has been turned over to city and county jurisdiction. After the opening of the expressway segment west of Moorland in December 2010, the west end was moved to the interchange with US 20 and County Road D36 northeast of Moorland. (Terminus
photos)
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