State Road 18 (SR 18) in the U.S. State of Indiana is an east–west route in North Central Indiana running from the Illinois border in Benton County almost to the Ohio border, terminating at U.S. Route 27 (US 27)/State Road 67 (SR 67) in Jay County. State Route 18 is mainly a 2 lane road with exception of 4 lane divided highway from Marion to Interstate 69 (I-69). Marion is the only considerably large city that Route 18 passes through.