Surname C
| SURNAME | TOWNSHIP | RESEARCHER |
| Cady |
Marilou West Ficklin | |
| Cantrall | Sharon L. Cantrall | |
| Capp⁄Kapp | Alan Weaver | |
| Carsten | Sandy Demlow | |
| Cashmore | Newport, Warren, Benton | Corky Bell |
| Chamberlin⁄Chamberlain | Waukegan | Molly Leonard |
| Chinn | Diane Boydstun | |
| Chorazak⁄Harazak | North Chicago | Edward Harazak |
| Christianson | Zion | Cynthia Solem |
| Christensen | Waukegan | Lennie Spinazola |
| Clark | Waukegan | Pat |
| Clarke | Antioch | Joey Clarke-Jordan Van Us |
| Cleaver | Waukegan & Warren Twp | Janice Buchanan |
| Cleveland | Waukegan, 1920s-1940s | Beth Blote |
| Cloes | Lake Bluff | Roger Peterson |
| Closson | Waukegan | Cheryl Cameron |
| Colby | Steve Regul | |
| Collet | Wauconda | Susan Edgell |
| Converse | Laura L. Riley | |
| Cooley | Bill Cooley | |
| Cooper | Mary Towner Hansen | |
| Cooper | 1875-1880 | Susan Cooper |
| Corbin | Shields⁄Vernon⁄Libertyville | Marleen Van Horne |
| Corcoran | Waukegan | C. Parrett |
| Courser⁄Corser | Janet | |
| Cox | John Paul Cox | |
| Cragg | Rita Breeding | |
| Crepas | Brenda | |
| Cribb | Laurie | |
| Cribb | Stephanie Osmachenko | |
| Crowley | Shields | Clare |
| Culleeney | Rosemary Duff | |
| Cummings | Shirley M. Cummings | |
| Cunningham | Shields Twp., 1840- | Catherine Green |
| Cunnington | Benton | Jay Cunnington |
| Curtis | Waukegan - 1850's | Gail Henry |