The St. Vrain massacre was an incident in the Black Hawk War. It occurred near present-day Pearl City, Illinois, in Kellogg's Grove, on May 24, 1832. The massacre was most likely committed by Ho-Chunk warriors who were unaffiliated with Black Hawk's band of warriors. It is also unlikely that the group of Ho-Chunk had the sanction of their nation. Killed in the massacre were United States Indian Agent Felix St. Vrain and three of his companions. Some accounts reported that St. Vrain's body was mutilated.

The Buffalo Grove ambush was an ambush that occurred on May 19, 1832 as part of the Black Hawk War. A six-man detail carrying dispatches from United States Colonel James M. Strode at Galena, Illinois to General Henry Atkinson at Dixon's Ferry was ambushed by Native Americans during the attack. William Durley was killed and buried near the site of the ambush. Durley's remains were initially interred by the party that would become victims of the St. Vrain massacre. Two other men had bullet holes in their clothing, but were uninjured. In 1910 the Polo Historical Society moved Durley's remains to a plot beneath a memorial they erected west of Polo, Illinois.