LAKE COUNTY CHURCH RECORDS
FamilySearch.org has microfilmed and digitized the Archdiocese of Chicago records to 1915. Lake County is part of the Archdiocese of Chicago and its records are included in this collection. Many of the digitized films contain an index for the records.
ILLINOIS CHURCH RECORDS
The FamilySearch Wiki page Illinois Church Records provides helpful background information on major religions in Illinois with links to repositories for many of them. Included is a map containing the boundaries for the Diocese’s in the state and the Archdiocese of Chicago.