(March 8–12, 1857), incident in northwestern Iowa, U.S., in which a band of Sioux Indians led by Inkpaduta killed more than 30 white people. In 1856 five cabins had been built and occupied by whites near Okoboji lakes and Spirit Lake. After a severe winter, the Sioux attacked, killed 32 men, women, and children on the spot and abducted four women, of whom two were subsequently killed, one released voluntarily, and one ransomed. A relief expedition sent from Ft. Dodge arrived only in time to bury the dead. Another, sent from Ft. Ridgely in Minnesota, pursued Inkpaduta, who fled westward, but failed to overtake him. The massacre was commemorated by a monument erected in 1895 at nearby Arnolds Park.