I-15 enters Bonneville County one mile before its interchange with West 65th South near Woodville, which is simply given the destination of "Exit 113" northbound. US 26 and I-15 Bus. split off onto Sunnyside Road shortly before I-15 enters Idaho Falls. The Interstate has a five-ramp partial cloverleaf interchange with US 20 (West Broadway Street), from which US 20 Bus. splits east concurrent with I-15 Bus., which returns to the mainline Interstate. I-15 and US 20 run concurrently to a four-ramp partial cloverleaf interchange where US 20 heads northeast as a freeway towards Ucon, Rigby, Rexburg, Sugar City, St. Anthony, Ashton, Island Park, West Yellowstone, and Yellowstone National Park. The Interstate heads north out of Idaho Falls parallel to the Montana Subdivision rail line, Old Highway 91, and the Snake River. I-15 enters Jefferson County just north of its diamond interchange with Osgood Road, and the freeway diverges from the Snake River at Roberts, where it has a diamond interchange with the western end of SH 48.