History and Timeline
History:

Chief Illiniwek was the University of Illinois at Urbana-Champaign's mascot from 1926 to February 21, 2007 when it had its last halftime performance. Chief Illiniwek was officially banned in 2007 because of the insistence of the NCAA since the university wouldn't be allowed to play at other schools or hold athletic events if they didn't remove the chief as their mascot.
The Illiniwek is known as being a complete human being. This human being is strong, agile human body, and the indomitable human spirit.
A student who represented the Illiniwek, which is the state's namesake, portrayed Chief Illiniwek. The costume that was worn came from the Sioux tribe. Frank Fools Crow, a chief of the Oglala Sioux, donated the costume that was worn by the mascot. It is known that the chief of the Oglala Sioux is completely unrelated to the Illiniwek. The dance that Chief Illiniwek would perform at halftime came from 'Indian Lore' studies. A group of university students who had been Eagle Scouts studied the fancy dance and then adopted it. The style of the dance originated from the Plains Indians, and many Native Americans at pow-wows practiced it. The dance that the Eagle Scouts studied has evolved as the years have gone by.
The controversy to the chief began between fans and alumni of the university. Many fans and alumni view the chief as part of the university's traditions, but there are also many people that don't view the chief that way. For example, there are Native American individuals and organizations, social scientists, and educators that view the mascot as cultural appropriation of indigenous images and rituals. They also believe that it perpetuates stereotypes about American Indian people. The NCAA policy also viewed Chief Illiniwek as hostile or abusive. Therefore, the NCAA banned the University of Illinois at Urbana-Champaign from full participation in postseason activities as long as they continued to have Chief Illiniwek as their mascot.
Timeline:
1926: October 30
1989: October
1989: November 14
1990: March
1990: October 11
1991: October 2
1992
1993: January
1994: April 8
1995: December 1
1998: March 30
2005: August
2007: February 16
2007: February 21