α. 1800s– Illinoian, 1800s– Illinoyian (nonstandard), 1900s– Illinoyan (nonstandard).
β.   1800s– Illinoisian (pronounced either as the α.  forms   are, or as  Brit. /ˌɪlᵻˈnɔɪzɪən/, U.S. 
/ˌɪləˈnɔɪziən/). 
γ.   1800s– Illinoisan (usually pronounced as the α.  forms   are, or occasionally as  Brit. /ˌɪlᵻˈnɔɪzən/, U.S. 
/ˌɪləˈnɔɪzən/).