U.S. Route 20 Business in Idaho Falls is overlapped by US 26. It begins at I-15 Exit 118 on West Broadway Street, and runs concurrent with the Interstate 15 Business Loop until the intersection with Yellowstone Avenue, where BL-15 turns south and US 20 BUS/US 26 turns north. Curving under a set of railroad bridges, the street name briefly changes to the Northgate Mile. The concurrency with US 26 ends when US 20 BUS turns north onto North Holmes Avenue, while US 26 continues along North Yellowstone Highway. The railroad line that the route previously ran under is encountered again at the intersection with East Anderson Street, where the tracks cross from the southwest corner to the northeast corner. A while after crossing a bridge over South Fork Willow Creek, North Holmes Avenue intersects 29th Road North, and suddenly gains the additional name of Lewisville Road. US 20 BUS ends at the diamond interchange with US 20 (Rigby Highway), known as Exit 310.
