Hamilton County, Ohio Roman Catholic Baptism Records - Early - 1849 Authored by Jeffrey G Herbert This index contains the names of over 17,500 Roman Catholic baptisms recorded in Cincinnati and Hamilton County, Ohio prior to January 1850. The source materials for this work are the microfilm copies of original baptismal registers which were kept by the individual parish churches, and are stored at the Archives of the Archdiocese of Cincinnati. Although the diocese was founded in 1821, the oldest surviving records in Hamilton County are for Holy Trinity Church and date to 1834. The surviving records for the first church, St. Peter in Chains Cathedral, begin in 1839. This index contains baptismal records of all ten existing Roman Catholic Churches in Hamilton County, Ohio prior to January 1850.