From Cedar Rapids, the route continued south and east by overlapping US 30 and Iowa 38 to Tipton. It also entirely replaced Iowa 74, which stretched from Tipton to Davenport. Through Davenport, the highway entered from the northwest along the aptly named Northwest Boulevard. Further into town, it intersected Kimberly Road and then transitioned onto Harrison Street. In downtown, the highway overlapped US 61 and US 67 along 4th Street, briefly along Gaines Street, and then along 2nd Street. Iowa 150 followed US 67 onto the Centennial Bridge where it ended at the state line over the Mississippi River. On the Illinois side of the bridge, US 150 began at the state line.