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/).