 Interstate 129 | |||||||
|---|---|---|---|---|---|---|---|
 I-129 highlighted in red | |||||||
| Route information | |||||||
| Auxiliary route of I-29 | |||||||
| Length | 3.50 mi[1][2] (5.63 km) Nebraska: 3.21 mi (5.17 km) Iowa: 0.286 mi (460 m) | ||||||
| Existed | November 22, 1976[3]–present | ||||||
| NHS | Entire route | ||||||
| Major junctions | |||||||
| West end |  US 20 in South Sioux City, Nebraska | ||||||
  US 75 / US 77 in South Sioux City, Nebraska | |||||||
| East end |  I-29 / US 20 / US 75 in Sioux City, Iowa | ||||||
| Location | |||||||
| Country | United States | ||||||
| States | |||||||
| Counties | |||||||
| Highway system | |||||||
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Interstate 129 (I-129) is an auxiliary Interstate Highway which connects South Sioux City, Nebraska, 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.
- ^ "Nebraska Highway Reference Log Book" (PDF). Nebraska Department of Roads. 2015. p. 270. Archived from the original (PDF) on January 2, 2017. Retrieved January 8, 2017.
- ^ "Road Network (Portal)" (ESRI shapefile). Ames: Iowa Department of Transportation. April 9, 2021. Retrieved April 18, 2021.
- ^ Iowa Department of Transportation. The National System of Interstate Defense Highways: 1956–1996.