Illinois State Route 40 is a north-south highway in Whiteside County. It runs mostly in the eastern portion of the county. It is the main highway through the Sterling Area. IL St Rt 40 passes through the following towns in Whiteside County. Deer Grove Rock Falls Sterling IL St Rt 40 is not multi-plexed in Whiteside County. IL St Rt 40 intersects the following highways in Whiteside County. Illinois State Route 172, near Deer Grove. Interstate 88, near Rock Falls. Illinois State Route 110, near Rock Falls. U.S. Rt. 30, at Rock Falls. Illinois State Route 2, at Sterling.
