US Route 34, while in Iowa, spans the width of the state from the Missouri River to the Mississippi River, forming the second main east-west highway north of Iowa's southern border. It serves the row of Iowa counties that's second from the southern border (the southernmost row of counties is connected by Iowa Route 2). US Route 34 first makes its way into Iowa by crossing the Missouri River near Plattsmouth, Nebraska. It's a four lane highway at first, but quickly shrinks down to a two-lane rural highway. US Route 34 stays a two-lane highway until Ottumwa, where it picks up Iowa Route 163. As Iowa Route 163 is a four-lane rural expressway for all of its length (outside of Des Moines), US Route 34 is a four-lane expressway for all of its time spent tagging along with Iowa Route 163. That time, by the way, lasts all the way until US Route 34 crosses the Mississippi River out of Burlington, Iowa, into Gulfport, Illinois. US Route 34 serves a lot of important locales in Iowa, including Red Oak, Creston, Osceola, Chariton, Ottumwa, Fairfield, Mount Pleasant, and Burlington.