In Illinois, US Route 34 runs from Burlington, Iowa, to just outside of Chicago. This gives it an alignment running from west-southwest to east-northeast. It runs through cities like Monmouth, Galesburg, Princeton, Mendota, Plano, and Naperville. It's a useful route in Chicago's western suburbs, where it's known as Ogden Avenue; outside of Chicagoland, US Route 34 follows the original BNSF rail line, now an Amtrak line, connecting Chicago and Burlington. The eastern end of the US highway is at Illinois 43 in Berwyn. That eastern terminus is an oddity, marking one of the few times a US highway ends at a state route.
US Route 34 first enters the state of Illinois crossing the Mississippi River from Burlington, Iowa:
Near Gladstone, US Route 34 meets the southwestern end of Illinois 164:
US Route 34 serves as an expressway with ramps to Illinois Routes 94 and 116, at Biggsville...
US Route 34 meets the Monmouth area and joins US Route 67 north, using an onramp that appears on the right and hooks around:
Illinois 164, which serves as a local alternate to US Route 34, joins US Routes 34 and 67 north and east...
On the north side of Monmouth, US Route 67 splits from US Route 34 to head north:
Shortly after that, Illinois 164 deviates from US Route 34, and both routes leave Monmouth in slightly different directions:
As US Route 34 reaches Galesburg, it becomes a fully-fledged freeway, and the exit to Main Street serves as the eastern end of Illinois 164and the northern end of Illinois 41: