| SURNAME | TOWNSHIP | RESEARCHER |
| Naber | Antioch | Lee Koenig |
| Nelson | Newport - 1850's to 1880 | Doni Wright |
| Niskey/Nimskey | Wauconda/Cuba | Susan Edgell |
| Nimsgern | Wauconda/Cuba | Susan Edgell |
| Nottingham | Warren | Carleen Brown |
| Novak | Waukegan; from early 1900s | Bridget |
| O'Connell | Warren, Shields | Susan Bright |
| Ogrin | Waukegan and North Chicago 1890-1934 (possibly earlier) | Jody Miller |
| Ogrin | Waukegan; early 1900s | Sherese Williams |
| O'Hara | Dave Kliss | |
| O'Keefe | Shields | Clare |
| Osmond | Antioch | Lee Koenig |
| Osburn/Orsburn/Oursbourn | Cecil Oursbourn | |
| Ostrowski | Shields & Waukegan Twp | Terri Miller |