
The census entries for surnames beginning with O:
| Surname | Given Name | Age | Birth Place | Precinct | Page/Line | ED | Notes |
| O'Brien | Charles M. | 30 | IN | Pasco | 6B/75 | 3-64 | |
| O'Brien | Henry B. | 28 | MN | Pasco | 15A/39 | 3-64 | |
| O'Brien | Lillian | 25 | MN | Pasco | 15A/40 | 3-64 | |
| O'Brien | William | 58 | PA | Pasco | 16B/59 | 3-64 | |
| O'Brien | Wm. | 57 | PA | Fishhook | 5A/8 | 3-63 | |
| Ochlochlarger | Carl | 8 | OR | Connell | 8A/11 | 3-60 | |
| Ochlochlarger | Emilie | 18 | WY | Connell | 8A/14 | 3-60 | |
| Ochlochlarger | Emma | 26 | OR | Connell | 8A/10 | 3-60 | |
| Ochlochlarger | Herman | 34 | Germany | Connell | 8A/9 | 3-60 | |
| Ochlochlarger | Lena | 2 | WA | Connell | 8A/12 | 3-60 | |
| Ochlochlarger | Paul | 27 | WY | Connell | 8A/13 | 3-60 | |
| O'Connor | Joseph A. | 23 | PA | Pasco | 14B/53 | 3-64 | |
| Odell | James I. | 34 | WI | Nunamaker | 7B/97 | 3-61 | |
| Okawa | Hiotoro | 25 | Japan | Pasco | 23B/52 | 3-64 | |
| Okemoto | Josie | 21 | Japan | Pasco | 23A/9 | 3-64 | |
| Okemoto | Toney | 31 | Japan | Pasco | 23A/8 | 3-64 | |
| Okugawa | Naritaro | 30 | Japan | Pasco | 23A/46 | 3-64 | |
| Oldenburg | Arthur | 11 | SD | Connell | 8B/56 | 3-60 | |
| Oldenburg | Herald | 8 | WA | Connell | 8B/57 | 3-60 | |
| Oldenburg | Louis | 18 | MN | Connell | 8B/54 | 3-60 | |
| Oldenburg | Maggie | 35 | WI | Connell | 8B/52 | 3-60 | |
| Oldenburg | Selma | 20 | WI | Connell | 8B/53 | 3-60 | |
| Oldenburg | Walter | 15 | AR | Connell | 8B/55 | 3-60 | |
| Oldenburg | William | 35 | WI | Connell | 8B/51 | 3-60 | |
| Olds | Catherine | 36 | IN | Connell | 13B/59 | 3-60 | |
| Olds | Edward | 44 | NE | Connell | 13A/24 | 3-60 | |
| Olds | Fern | 3 | WA | Connell | 13B/63 | 3-60 | |
| Olds | Florida | 23 | NE | Connell | 13B/65 | 3-60 | |
| Olds | John | 67 | IN | Connell | 13A/26 | 3-60 | |
| Olds | Josie | 34 | Bohemia | Connell | 13A/25 | 3-60 | |
| Olds | Laura | 14 | NE | Connell | 13B/61 | 3-60 | |
| Olds | Lon | 12 | NE | Connell | 13B/62 | 3-60 | |
| Olds | Mary | 66 | MO | Connell | 13A/27 | 3-60 | |
| Olds | Otto | 17 | NE | Connell | 13B/60 | 3-60 | |
| Olds | Robert | 45 | MO | Connell | 13B/58 | 3-60 | |
| Olds | Tay | 4/12 | WA | Connell | 13B/64 | 3-60 | Given name illegible |
| Olson | Irene E. | 11/12 | WA | Pasco | 17A/15 | 3-64 | |
| Olson | Irving R. | 11/12 | WA | Pasco | 17A/16 | 3-64 | |
| Olson | Matilda | 26 | Sweden | Pasco | 17A/14 | 3-64 | |
| Olson | Peter | 28 | Sweden | Pasco | 16A/18 | 3-64 | |
| Olson | Raymond | 30 | UT | Pasco | 17A/13 | 3-64 | |
| Olush | William | 50 | Unknown | Connell | 14A/3 | 3-60 | Surname unclear |
| Onapach | Charles H. | 42 | IN | Kahlotus | 2A/6 | 3-61 | |
| Onapach | Clara K. | 32 | OH | Kahlotus | 2A/7 | 3-61 | |
| Onapach | Clarance C. | 1 1/2 | WA | Kahlotus | 2A/9 | 3-61 | |
| Onapach | Tillman P. | 3 | WA | Kahlotus | 2A/8 | 3-61 | |
| O'Neil | William G. | 27 | PA | Pasco | 4B/56 | 3-64 | |
| O'Neill | Bertha J. | 25 | MN | Pasco | 13B/66 | 3-64 | |
| O'Neill | James H. | 35 | WI | Pasco | 13B/65 | 3-64 | |
| Ong | Chin | 49 | China | Pasco | 22B/72 | 3-64 | |
| Ong | Fook | 56 | China | Pasco | 22B/79 | 3-64 | |
| Ong | Fun | 66 | China | Pasco | 22B/75 | 3-64 | |
| Ong | Gat | 50 | China | Pasco | 22A/9 | 3-64 | |
| Ong | Kong | 52 | China | Pasco | 22A/46 | 3-64 | |
| Ong | Sam | 60 | China | Pasco | 22B/93 | 3-64 | |
| Ong | San | 68 | China | Pasco | 21B/82 | 3-64 | |
| Ong | Toy | 43 | China | Pasco | 22A/45 | 3-64 | |
| Ong | Wang Fong | 52 | China | Pasco | 22B/98 | 3-64 | |
| O'Niel | William | 53 | Ireland | Pasco | 16B/61 | 3-64 | |
| Ono | Toshio | 23 | Japan | Pasco | 23A/24 | 3-64 | |
| Onzoi | Kichiraku | 35 | Japan | Pasco | 23A/25 | 3-64 | |
| O'Rourke | Felix | 28 | Ireland | Pasco | 15B/78 | 3-64 | |
| Ortell | Delilia | 12 | WA | Pasco | 20B/64 | 3-64 | |
| Ortell | Ella | 32 | IA | Pasco | 20B/63 | 3-64 | |
| Ortell | George H. | 42 | NJ | Pasco | 20B/62 | 3-64 | |
| Ortell | Georgie | 6 | WA | Pasco | 20B/65 | 3-64 | |
| Ortell | Thomas | 11/12 | WA | Pasco | 20B/66 | 3-64 | |
| Ortolf | Barbara | 58 | Germany | Pasco | 4A/1 | 3-64 | |
| Ortolf | George W. | 17 | MN | Pasco | 4A/2 | 3-64 | |
| Osborne | Edith B. | 26 | IN | Pasco | 14A/15 | 3-64 | |
| Osborne | Harry B. | 30 | NY | Pasco | 14A/14 | 3-64 | |
| Osborne | Huston | 4 | MN | Pasco | 14A/16 | 3-64 | |
| Oschner | Wilfred L. | 24 | MN | Pasco | 4B/78 | 3-64 | |
| Osterland | George | 42 | MN | Kahlotus Town | 1B/77 | 3-61 | |
| Overman | Charley | 26 | OK | LeRoy | 5A/17 | 3-62 | |
| Overman | Nathan | 39 | KS | LeRoy | 5A/18 | 3-62 | |
| Overturf | Agness S. | 40 | Canada | LeRoy | 4A/27 | 3-62 | |
| Overturf | William R. | 40 | IN | LeRoy | 4A/26 | 3-62 | |
| Owens | Della M. | 26 | WA | Fishhook | 5A/17 | 3-63 | |
| Owens | Edward | 46 | CA | Kahlotus | 5A/28 | 3-61 | |
| Owens | Elsie M. | 11 | WA | Fishhook | 5A/18 | 3-63 | |
| Owens | Milly J. | 3 | WA | Fishhook | 5A/20 | 3-63 | |
| Owens | Oley L. | 9 | WA | Fishhook | 5A/19 | 3-63 | |
| Owens | Wm. L. | 42 | WA | Fishhook | 5A/16 | 3-63 | |
| Oyama | Sanshichi | 28 | Japan | Pasco | 23A/41 | 3-64 |