Roman Catholics constitute the single largest religious denomination in Illinois; they are heavily concentrated in and around Chicago, and account for nearly 30% of the state's population. However, taken together as a group, the various Protestant denominations comprise a greater percentage of the state's population than do Catholics. In 2000 Catholics in Illinois numbered 3,874,933, the largest Protestant denominations were the United Methodist Church, with 365,182 members, and the Southern Baptist Convention, with 305,838. The largest non-Christian group were Jews with 270,000. Chicago and its suburbs are also home to a large and growing population of Hindus, Muslims, Baha'is and Sikhs.
Illinois played an important role in the early Latter Day Saint movement, with Nauvoo, Illinois, becoming a gathering place for Mormons in the early 1840s. Nauvoo was the location of the succession crisis, which led to the separation of the Mormon movement into several Latter Day Saint sects. The Church of Jesus Christ of Latter-day Saints, the largest of the sects to emerge from the Mormon schism, claims 55,460 in Illinois today.
|2000 (total population)||80.71%||15.73%||0.62%||3.84%||0.11%|
|2000 (Hispanic only)||11.78%||0.35%||0.19%||0.08%||0.04%|
|2005 (total population)||80.34%||15.63%||0.62%||4.45%||0.11%|
|2005 (Hispanic only)||13.72%||0.39%||0.20%||0.09%||0.04%|
|Growth 2000–05 (total population)||2.30%||2.07%||3.74%||19.16%||10.13%|
|Growth 2000–05 (non-Hispanic only)||-0.68%||1.81%||0.91%||19.36%||10.18%|
|Growth 2000–05 (Hispanic only)||19.75%||13.28%||10.14%||9.96%||10.06%|
|* AIAN is American Indian or Alaskan Native; NHPI is Native Hawaiian or Pacific Islander|