 As a consequence of an 1804 treaty between the governor of Indiana Territory and a group of Sauk and Fox leaders regarding land settlement , the tribes vacated their lands in Illinois and moved west of the Mississippi in 1828 . However , Sauk Chief Black Hawk and others disputed the treaty , claiming that the full tribal councils had not been consulted , nor did those representing the tribes have authorization to cede lands . Angered by the loss of his birthplace , between 1830 – 31 Black Hawk led a number of incursions across the Mississippi River into Illinois , but was persuaded each time to return west without bloodshed . In April 1832 , encouraged by promises of alliance with other tribes and the British , he again moved his so @-@ called " British Band " of around 1 @,@ 000 warriors and non @-@ combatants into Illinois . Finding no allies , he attempted to return across the Mississippi ( to present @-@ day Iowa ) , but the undisciplined Illinois Militia 's actions led to the Battle of Stillman 's Run . A number of other engagements followed , and the militia of Michigan Territory and the state of Illinois were mobilized to hunt down Black Hawk 's band . The conflict became known as the Black Hawk War . 
