| Oregon Federal Census Index 1900 | ||||
| Baker County | Series T623 | |||
| Name | Precinct | ED No. | Sheet No. | Line No. |
| Oakley, Benjiman F. | Baker City Ward 4 | 162 | 15 | 3 |
| O Dell, Bird | Parker | 181 | 2 | 41 |
| O Dell, Charles P. | Parker | 181 | 2 | 43 |
| O Dell, Mathew | Parker | 181 | 2 | 40 |
| O Dell, Thomas F. | Parker | 181 | 2 | 42 |
| Odesby, William H. | Parker | 181 | 3 | 51 |
| O'Dowd, Patrick J. | Parker | 181 | 2 | 19 |
| O'Hara, Kate | Baker City Ward 1 | 162 | 8 | 88 |
| Olbrick, Adelhia | Baker City Ward 2 | 162 | 3 | 74 |
| Olbrick, Amelia J. | Baker City Ward 2 | 162 | 3 | 100 |
| Olbrick, Annalee | Baker City Ward 2 | 162 | 4 | 1 |
| Olbrick, Caroline H. | Baker City Ward 2 | 162 | 3 | 98 |
| Olbrick, Charles | Baker City Ward 2 | 162 | 3 | 75 |
| Olbrick, Francis, J. | Baker City Ward 2 | 162 | 4 | 3 |
| Olbrick, John | Baker City Ward 2 | 162 | 3 | 97 |
| Olbrick, John R. | Baker City Ward 2 | 162 | 3 | 99 |
| Olbrick, Mary C. | Baker City Ward 2 | 162 | 4 | 2 |
| Olbrick, Pauline M. | Baker City Ward 2 | 162 | 4 | 4 |
| Oliver, Arthur D. | Baker City Ward 4 | 162 | 14 | 27 |
| Oliver, Charles H. | Baker City Ward 4 | 162 | 14 | 26 |
| Oliver, George S. | Baker City Ward 4 | 162 | 14 | 29 |
| Oliver, Jennie S. | Baker City Ward 4 | 162 | 14 | 28 |
| Oliver, John W. | Baker City Ward 4 | 162 | 14 | 25 |
| Olmsted, Belia E. | Baker City Ward 1 | 162 | 6 | 46 |
| Olmsted, Harland H. | Baker City Ward 1 | 162 | 6 | 48 |
| Olmsted, Martin | Baker City Ward 1 | 162 | 6 | 45 |
| Olmsted, Percy N. | Baker City Ward 1 | 162 | 6 | 47 |
| Olsen, Edward A. | Baker City Ward 1 | 162 | 10 | 6 |
| Olsen*, John | Baker City Ward 1 | 162 | 7 | 41 |
| O'Malley, Bridget | Baker City Ward 1 | 162 | 13 | 59 |
| O'Neil, Constantine | Baker City Ward 1 | 162 | 13 | 71 |
| Orchard, John H. | Parker | 181 | 4 | 27 |
| Osborn, Beatrice B. | Baker City Ward 4 | 162 | 16 | 85 |
| Osborn, Dolorus H. | Baker City Ward 4 | 162 | 16 | 87 |
| Osborn, Ella B. | Baker City Ward 4 | 162 | 16 | 84 |
| Osborn, Irwin S. | Baker City Ward 4 | 162 | 16 | 83 |
| Osborn, Ronald | Baker City Ward 4 | 162 | 16 | 86 |
| Osborne, John | Parker | 181 | 4 | 4 |
| Oswell, John | Parker | 181 | 2 | 17 |
| Oswell, Mary | Parker | 181 | 2 | 18 |
| Owen, William | Rock Creek | 176 | 5 | 34 |