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. later, I-129/US 20/US 75 intersect Dakota Avenue at a partial cloverleaf interchange. 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. 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 of Interstate Highway was allocated to the states. Iowa received the smallest allocation, , for the southern bypass of Sioux City. The proposed highway was planned to cost $22.5 million (equivalent to $ million in ), which included $15 million (equivalent to $ million in ) for the Missouri River bridge. On the 1973 state highway map, the Iowa State Highway Commission showed the planned route on the state map for the first time. I-129 was opened on November 22, 1976.Exit list
References
{{s-end 29-1 29-1 29-1 U.S. Route 20 U.S. Route 75 1 Transportation in Dakota County, Nebraska Transportation in Woodbury County, Iowa