Index To McHenry County Death Certificates, Book I – Dec 1877- 16 Apr 1909
| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | XY | Z |
| Surname | First Name | Certificate Number | Notes |
|---|---|---|---|
| O'BRIEN | Catherine | 1452 | - |
| O'BRIEN | Dennis | 2005 | - |
| O'BRIEN | Margaret Denovan | 173 | - |
| O'BRIEN | Martin | 1431 | - |
| O'BRIEN | Michael | 2696 | - |
| O'BRIEN | Patrick | 785 | - |
| O'BRINE | Mrs Mary | 2788 | - |
| O'CONNOR | Charles | 583 | - |
| O'CONNOR | Johnie | 46 | - |
| O'CONNOR | Peter | 1554 | - |
| O'CONOR | Frank | 637 | - |
| O'ERKEL | Henry Peter | 2695 | - |
| O'HERN | John Donald | 2977 | - |
| O'LEARY | Dan | 1383 | - |
| O'LEARY | Daniel | 1781 | - |
| O'NEIL | Edward | 2188 | - |
| O'NEIL | Ella | 2630 | - |
| O'NEIL | Harriet R | 1902 | - |
| O'NEIL | Patrick M | 2504 | - |
| O'ROURK | Agnes | 319 | Indexed as ROURKE, Anges O |
| O'ROURK | Daniel | 1321 | - |
| OAKFITZ | Lena Recka Minne | 766 | - |
| OAKLEY | George | 1832 | - |
| OAKLEY | Virginia Hudson | 2638 | - |
| OBERST | Jacob | 2921 | - |
| OBERST | Wilhelmina | 2282 | - |
| OCENASEK | Frank | 1909 | - |
| OEFFLING | Anna | 325 | - |
| OEFFLING | Leonard | 542 | - |
| OERKFITZ | Alfred | 2593 | - |
| OERKFITZ | Christian | 1355 | - |
| OERTEL | - | 2912 | Infant Male |
| OEST | Lucy | 237 | - |
| OLESEN | Isabell | 1497 | - |
| OLESEN | Matilda W | 1258 | - |
| OLMSTEAD | Pinnah | 677 | - |
| OLSON | Charles Edward | 1938 | - |
| OPATNARY | Theodore | 2356 | - |
| ORCUTT | Gilbert Sam'l | 2881 | - |
| ORMSBEE | C Adeline | 2111 | - |
| OSBORNE | Angeline | 1107 | - |
| OSMOND | Anna | 2838 | - |
| OSMOND | Unnamed child of George and Harriett | 657 | Female |
| OSTERHOUT | John | 950 | - |
| OSTRANDER | Estella | 1293 | - |
| OTIS | Jamie | 871 | - |
| OTTO | Rudolph W | 2914 | - |
| OVERTON | Addie A | 630 | - |
| OVETON | James S | 1884 | - |
| OVERTON | Ruth | 313 | - |
| OWEN | Oiver Wm | 2059 | - |
