Interstate 129

Interstate 129
Interstate 129
	I-129 highlighted in red
Route information
	Auxiliary route of I-29
Length	3.50 mi (5.63 km) Nebraska: 3.21 mi (5.17 km); Iowa: 0.286 mi (0.460 km)
Existed	November 22, 1976–present
Major junctions
West end	US 20 / US 75 / US 77 in South Sioux City, NE
	US 77 in South Sioux City, NE
East end	I-29 / US 20 / US 75 in Sioux City, IA
Location
States	Nebraska; Iowa;
Counties	NE Dakota; ; IA Woodbury; ;
Highway system
	Interstate Highway System; Main; Auxiliary; Suffixed; Business; Future;

Interstate 129 (I-129) is an auxiliary Interstate Highway which connects South Sioux City to I-29 in Sioux City, Iowa. Opened in 1976, I-129 is a 3.5-mile-long (5.6 km) route, running 3.21 miles (5.17 km) in Nebraska. At 0.286 miles (0.460 km), I-129 is the shortest highway in the state of Iowa. All of the route's length is concurrent with U.S. Route 20 (US 20) and most of its length is concurrent with US 75. I-129 is also one of only four auxiliary Interstate Highways to go into a state its parent route does not.

Route description[]

I-129 begins along US 20 on the western edge of South Sioux City, Nebraska, just west of exit 1, a cloverleaf interchange with US 75 and US 77. US 77 travels north through South Sioux City before ending at I-29 in Sioux City while US 75 joins I-129 and US 20. One mile (1.6 km) later, I-129/US 20/US 75 intersect Dakota Avenue at a partial cloverleaf interchange.^[2] U.S. Highway 20 Business (US 20 Bus.) is designated along Dakota Avenue.

East of Dakota Avenue, I-129/US 20/US 75 travels south of South Sioux City and passes through rolling farmland. For the rest of I-129's length, the two directions of I-129/US 20/US 75 traffic are separated by a Jersey barrier instead of a grassy median. The three routes cross the Missouri River and immediately intersect I-29 at an interchange. Due to the minimum amount of space along the Missouri River banks, the I-29 interchange is a modified two-level cloverstack interchange.^[4] At I-29, US 20 and US 75 continue east around Sioux City and I-129 ends.

History[]

After the passage of the Federal-Aid Highway Act in 1968, the mileage which would eventually be manifested in over 1,400 miles (2,300 km) of Interstate Highway was allocated to the states. Iowa received the smallest allocation, 0.5 miles (0.80 km), for the southern bypass of Sioux City.^[5] The proposed highway was planned to cost $22.5 million (equivalent to $139.21 million in 2020), which included $15 million (equivalent to $92.8 million in 2020) for the Missouri River bridge.^[6] On the 1973 state highway map, the Iowa State Highway Commission showed the planned route on the state map for the first time.^[7] I-129 was opened on November 22, 1976.^[1]

Exit list[]

State	County	Location	mi^[2]^[3]	km	Exit	Destinations	Notes
Nebraska	Dakota		0.00	0.00		US 20 west	Western end of US 20 overlap; continuation beyond western terminus
			0.38– 0.40	0.61– 0.64	1	US 75 south / US 77 – Fair Grounds, Sioux City	Western end of US 75 overlap; signed as exits 1A (south) & 1B (north).
		South Sioux City	1.50	2.41	2	US 20 Bus. east – South Sioux City, Dakota City
Missouri River			3.21 0.000	5.17 0.000	Sergeant Floyd Memorial Bridge; Nebraska–Iowa line
Iowa	Woodbury	Sioux City	0.286	0.460	1	I-29 / US 75 Bus. – Council Bluffs, Sioux Gateway Airport, Downtown Sioux City	Eastern terminus; eastern end of US 20/US 75 overlap; signed as exits 1A (south) and 1B (north); I-29 exits 144A-B
Iowa	Woodbury	Sioux City	0.286	0.460		US 20 east / US 75 north – Fort Dodge, Le Mars	Continuation beyond I-29
1.000 mi = 1.609 km; 1.000 km = 0.621 mi Concurrency terminus

References[]

^ ^a ^b Iowa Department of Transportation. The National System of Interstate Defense Highways: 1956–1996.
^ ^a ^b ^c "Nebraska Highway Reference Log Book" (PDF). Nebraska Department of Roads. 2015. p. 270. Retrieved January 8, 2017.
^ ^a ^b "Road Network (Portal)" (ESRI shapefile). Ames: Iowa Department of Transportation. April 9, 2021. Retrieved April 18, 2021.
^ Google (February 27, 2010). "Interstate 129" (Map). Google Maps. Google. Retrieved February 27, 2010.
^ Federal Highway Administration. "FHWA By Day - December 13". Retrieved August 1, 2010.
^ "Hot off the Wire". Carroll Daily Times Herald. Carroll, Iowa. June 2, 1972. p. 2. Retrieved August 9, 2014 – via Newspapers.com.
^ Iowa State Highway Commission (1973). State of Iowa Transportation Map (PDF) (Map). Ames: Iowa State Highway Commission. Sioux City inset. Retrieved August 1, 2010.

( • help)

Browse numbered routes
← Iowa 128	IA	→ Iowa 130
← N-128	NE	→ N-133

[DOT_Interstates-1] Iowa Department of Transportation. The National System of Interstate Defense Highways: 1956–1996.

[NDOR-2] "Nebraska Highway Reference Log Book" (PDF). Nebraska Department of Roads. 2015. p. 270. Retrieved January 8, 2017.

[DOTGIS-3] "Road Network (Portal)" (ESRI shapefile). Ames: Iowa Department of Transportation. April 9, 2021. Retrieved April 18, 2021.

[4] Google (February 27, 2010). "Interstate 129" (Map). Google Maps. Google. Retrieved February 27, 2010.

[FHWA_Dec_13-5] Federal Highway Administration. "FHWA By Day - December 13". Retrieved August 1, 2010.

[6] "Hot off the Wire". Carroll Daily Times Herald. Carroll, Iowa. June 2, 1972. p. 2. Retrieved August 9, 2014 – via Newspapers.com.

[DOT1973-7] Iowa State Highway Commission (1973). State of Iowa Transportation Map (PDF) (Map). Ames: Iowa State Highway Commission. Sioux City inset. Retrieved August 1, 2010.

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