Union County is a county located in the southern part of the U.S. state of Iowa. As of the 2020 Census, the population was 12,138. The county seat is Creston. Organized at a time of tensions before the Civil War, the county was named in 1853 for the union that people wanted to preserve. Union County peaked in population at the 1900 Census. Its economy is based on agriculture and related industries.

U.S. Highway 34 (US 34) is a United States Highway that runs across the southern third of Iowa. It begins on a bridge over the Missouri River west of Glenwood and travels east where it meets Interstate 29 (I-29) and US 275. Through southwestern Iowa, the highway is, for the most part, a two-lane rural road with at-grade intersections; there are interchanges with US 59 near Emerson and US 71 near Stanton and Villisca. At Osceola, the highway intersects I-35 and US 69. Just east of Ottumwa, where the road meets US 63, the road joins the four-lane Iowa 163 for the remainder of its trek through the state. At Mount Pleasant, it overlaps US 218 and Iowa 27, the Avenue of the Saints Highway. From there, the road heads to the southeast where it crosses the Mississippi River on the Great River Bridge at Burlington.