Swarms of grasshoppers invaded this county in July 1876, destroyed two-thirds of the crop, and laid millions of eggs. A grain farm at this site was owned by Paul Willmar, son of Leon Willmar, after whom the city was named. Willmar and other farmers tried, among other things, digging trenches to bury the hoppers. In 1877 grasshoppers ate the newly emerging grain. Farmers were left destitute, and the State Legislature passed "The Law to Furnish Seed Grain for Grasshopper Sufferers" in 1878. Part of the former Willmar farm eventually became the State Hospital Farm, opened in 1912 and later called the Regional Treatment Center.