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| Name | Date of Death | Location | Age | Gender |
| O'Hair, Edgar | 23-Jul-1906 | Brookville | 54 yr | Male |
| O'Hair, John Dempsey | 28-Nov-1914 | Laurel | 61 yr | Male |
| O'Neil, Sister Euphrasia | 27-Jan-1906 | Oldenburg | 57 yr | Female |
| Oberhaus, Marie | 1-Feb-1905 | Hamburg | 11 mon | Female |
| Obermeyer, Joseph | 6-Dec-1902 | Ray Township | 65 yr | Male |
| Obermeyer, Mary C. | 24-Nov-1900 | Ray Township | 38 yr | Female |
| Obyrn, George F. | 9-Dec-1917 | Brookville | 69 yr | Male |
| Odell, James | 8 Apr 1897 | Poor Asylum | 82 yr | Male |
| Ogar, Ed | 11 Jun 1899 | Whitcomb | 26 yr | Male |
| Ogden, Edgar W. | 13-Mar-1913 | Fairfield | 44 yr | Male |
| Ogden, Henry | 7-Jun-1917 | Fairfield | 46 yr | Male |
| Ogle, Jane | 10 Aug 1882 | Fairfield Township | 67 yr | Female |
| Ogle, William Alexander | 3-Mar-1900 | Cedar Grove | 65 yr | Male |
| Oldmin, Charlott | 1 Mar 1894 | Brookville | 78 yr | Male |
| Oliphant, Hiram M. | 3-Aug-1911 | Laurel Township | 62 yr | Male |
| Oliphant, Mary J. | 1-May-1907 | Metamora Township | 80 yr | Female |
| Oliphant, Richard | 12-Apr-1902 | Metamora | 49 yr | Male |
| Ortman, Joseph | 20-Jan-1916 | Ray Township | 76 yr | Male |
| Osborn, Babe Francis | 12-Feb-1912 | Fairfield | Female | |
| Osborn, Lizzie | 11-Nov-1902 | Poor Asylum | 66 yr | Female |
| Osborn, Martha F. | 9-Mar-1901 | Brookville | 58 yr | Female |
| Osborn, Mary | 14 Feb 1887 | Saint Marys | 35 yr | Female |
| Osborn, Squire | 19-Dec-1917 | Butler Township | 80 yr | Male |
| Osborn, Susan | 18-Dec-1919 | Fairfield Township | 69 yr | Female |
| Osborn, Tyrus | 29-Oct-1915 | Butler Township | 7 mon | Male |
| Osborn, William | 27-May-1908 | Butler Township | 74 yr | Male |
| Osburn, Eliza | 16 Mar 1899 | Fairfield | 85 yr | Female |
| Osburn, George Riley | 20-Nov-1909 | Brookville Township | 81 yr | Male |
| Osgood, Albert | 23 Mar 1898 | Brookville | 51 yr | Male |
| Osgood, Isaac | 25-Mar-1913 | Brookville | Male | |
| Ostheimer, Andrew | 25-Mar-1913 | Brookville | Male | |
| Osthimer, Leo | 24 Apr 1888 | Cedar Grove | 19 yr | Male |
| Ostrowsky, M. Rufina | 6-Jun-1908 | Oldenburg | 23 yr | Female |
| Oswald, Catherina | 6-May-1909 | Oldenburg | 82 yr | Female |
| Oswald, Jacob | 28-Oct-1910 | Oldenburg | 82 yr | Male |
| Oswald, John | 18-Jun-1904 | Butler Township | 45 yr | Male |
| Ott, Caroline Catherine | 7-Nov-1919 | Laurel Township | 82 yr | Female |
| Ott, Frederick | 19-Mar-1914 | Laurel Township | 76 yr | Male |
| Otten, Barney | 8-Apr-1901 | Saint Peters | Male | |
| Otten, Katherine | 8-Dec-1919 | Ray Township | 87 yr | Female |
| Otto, Anna M.M. | 31-Aug-1904 | Brookville | 36 yr | Female |
| Otto, Harvey | 25-May-1907 | Brookville | 75 yr | Male |
| Overmyer, Maria | 8-Dec-1908 | Ray Township | 62 yr | Female |
| Owens, Mary | 19 Nov 1882 | Springfield | 70 yr | Female |
| Owens, Robert J. | 22-Dec-1904 | Brookville Township | 62 yr | Male |
| Oyler, Frances M. | 6-May-1903 | Brookville Township | 14 yr | Female |