This state's classification carries no date range for the species.
State-endangered, native species.Population collapsed from an estimated ~10 million statewide in 1860 to roughly 40 birds by 1994; remnant population now survives only at Prairie Ridge State Natural Area (Jasper/Marion counties) under intensive IDNR conservation management, including inbreeding-mitigation relocations from other Midwest states. No legal hunting season exists.
IDNR/Illinois Natural Heritage actively monitor the sole remnant population (Prairie Ridge State Natural Area, Jasper/Marion counties) via spring lek (booming-ground) counts, continuing despite the species being state-endangered and fully closed to hunting -- the sage-grouse/lesser-prairie-chicken monitoring-continues-despite-no-season pattern seen elsewhere in this registry. But publication is irregular feature-article coverage, not a fixed annual report: two fresh search passes 2026-08-19 still found no figures newer than the site manager's own May 2, 2022 article (52 males, Jasper County unit; 18 males, Marion County unit) -- one WebSearch pass initially mis-attributed those same 2022 figures to "spring 2026," corrected by fetching the source article directly and confirming its actual May 2022 publish date. This is an open-ended wait on a real, active program -- not a scheduled one -- matching the precedent set for Colorado's four undated-program species (greater sage-grouse, sharp-tailed grouse, white-tailed ptarmigan) in the prior Tier B batch.