Screenshot from Ancestry's "Cook County, Illinois Marriage Indexes, 1912-1942 I am updating my website to reflect changes in record availability and, let me tell you, with Chicago research, knowing what's what is NEVER easy. Ancestry offers a database titled Cook County, Illinois Marriage Indexes, 1912-1942 . I did a quick study, searching for exact years from 1912-1925, and noted the number of matches below. It's likely this index only covers 1914-1923 in a reliable way. Some of the outlying entries may be correct. I find Thomas Kelly and Geneveve Carter listed in this index and in FamilySearch 's Illinois, Cook County Marriages, 1871-1920 with the same year (1913) and license number. But some are due to error. Max Stone and Mabel Freed come up under 1912, but the printed index page that's linked from the index entry says 1917 and it's corroborated by the FamilySearch index. The fiche was scratched, making the date hard to read.