(Optical Illusion, IA-12-34) S. of Shell Rock, Shell Rock Township, Butler County, IA. Willow Av. S. 1.1 miles from jct with Cherry St. SW of Shell Rock to the quilt on the E. side of the road. Elso Reints. (N42 41.092 W92 35.586) Photos by Jack & June Schmidt 7-9-12.