Iowa 141. As it approaches the Sioux City metro area, it passes the Sioux Gateway Airport at Sergeant Bluff. At the Singing Hills Boulevard interchange, northbound is joined by southbound U.S. Highway 75 Business (US 75 Bus.). later, US 75 Bus. ends at the cloverleaf interchange with US 20/US 75, which is also the eastern end of I-129. For the next north of the I-129 interchange, I-29 runs closely, as close as , to the Missouri River. The Interstate follows the curve of the river and turns to the west. It meets Gordon Drive, which carries US 20 Bus. US 20 Bus. traffic is directed onto the Interstate for before it exits via a volleyball interchange, which represents the national northern end of US 77. I-29 continues west along the Missouri River, and, after the Big Sioux River converges into the Missouri, I-29 follows the Big Sioux. Shortly before it crosses the Big Sioux into South Dakota, Iowa 12 splits away to the north. History Construction of I-29 began in the late 1950s in the Sioux City area. The first section to open, a stretch from the Big Sioux River to the then–US 20/US 77 bridge across the Missouri River opened around October 1, 1958. In September 1961, I-29 was extended across the Big Sioux River to South Dakota. On April 1, 1962, some of the northbound directional spans collapsed into the Big Sioux River at the South Dakota state line as a result of flooding and bridge scour. North of Council Bluffs, a section to Missouri Valley opened in November 1958. By December 1967, the two sections were connected, creating of continuous interstate highway. Due to a shortage of male workers, at least 20 women were enlisted to help build this section of I-29. The women were paid $2.00 hourly (equivalent to $ hourly in ), the same wage as men would have earned. Construction of I-29 in the Council Bluffs area was completed in 1970, and the route was open to Glenwood in the same year. Additional interchanges were added in the Sioux City and Council Bluffs areas between 1970 and 1971. The last of Interstate were constructed and opened in sections over the next two years; the last section opened on December 15, 1972. In 1973, US 34 was expanded to four lanes near Glenwood, which resulted in US 34 being rerouted onto I-29 for . In