Residents of Hamilton, Ward—Quartier No. 3 — Sub-district C, surnames O (1881 Census)
| # | Surname | Given | Sex | Age | Religion | Origin | Birthplace | Occupation | HH |
| 16 | oberlin | bertha | F | 20 | Methodist | German | Ontario | Servants nfs | 334 |
| 23 | obermeyer | catherine | F | 40 | Roman Catholic | Irish | Ireland | Tailors and tailoresses | 287 |
| 24 | obermeyer | henry | M | 19 | Roman Catholic | German | Ontario | Printers nfs | 287 |
| 1 | obermeyer | mary | F | 16 | Roman Catholic | German | Ontario | Milliners | 287 |
| 22 | obermeyer | matteron | M | 51 | Roman Catholic | German | France | Piano Makers | 287 |
| 25 | obermeyer | phillip | M | 17 | Roman Catholic | German | Ontario | No Occupation Listed | 287 |
| 20 | obrian | ann | F | 21 | Roman Catholic | Irish | Ontario | Servants nfs | 22 |
| 21 | obrien | edith | F | 0 | Roman Catholic | Irish | Ontario | No Occupation Listed | 282 |
| 7 | obrien | mary | F | 69 | Roman Catholic | Irish | Ireland | Farm workers (dairy) | 229 |
| 20 | obrien | mary | F | 2 | Roman Catholic | Irish | Ontario | No Occupation Listed | 282 |
| 19 | obrien | susan | F | 29 | Roman Catholic | Irish | Ireland | No Occupation Listed | 282 |
| 18 | obrien | william | M | 32 | Roman Catholic | Irish | United States | Boot and shoemakers and repairers | 282 |
| 9 | odell | richard | M | 21 | Anglican | English | England | Engineers (US) nfs | 286 |
| 24 | ogden | jennie | F | 21 | Anglican | English | Ontario | Servants nfs | 488 |
| 13 | oliver | david | M | 27 | Presbyterian | Scottish | Ontario | Ships Masters and captains (Sea or Inland Waterways) | 293 |
| 15 | oliver | elizabeth | F | 22 | Anglican | Scottish | Ontario | No Occupation Listed | 293 |
| 14 | oliver | mary | F | 55 | Presbyterian | Scottish | Scotland | No Occupation Listed | 293 |
| 21 | oliver | thomas | M | 34 | Anglican | English | England | Commercial travellers | 227 |
| 25 | olliver | anna | F | 50 | Anglican | English | England | No Occupation Listed | 484 |
| 18 | olliver | annie | F | 0 | Anglican | English | Ontario | No Occupation Listed | 404 |
| 15 | olliver | cyrus | M | 24 | Anglican | English | England | Occupational title unclassifiable | 404 |
| 1 | olliver | emma | F | 13 | Anglican | English | Ontario | No Occupation Listed | 484 |
| 17 | olliver | john | M | 2 | Anglican | English | Ontario | No Occupation Listed | 404 |
| 16 | olliver | sarah | F | 21 | Anglican | English | England | No Occupation Listed | 404 |
| 24 | olliver | thomas | M | 59 | Anglican | English | England | Occupational title unclassifiable | 484 |
| 13 | olmsted | charles | M | 2 | Methodist | German | Ontario | No Occupation Listed | 68 |
| 10 | olmsted | charlote | F | 33 | Methodist | German | Ontario | No Occupation Listed | 68 |
| 12 | olmsted | claretta | F | 5 | Methodist | German | Ontario | No Occupation Listed | 68 |
| 11 | olmsted | joseph | M | 7 | Methodist | German | Ontario | No Occupation Listed | 68 |
| 9 | olmsted | russell | M | 36 | Methodist | German | Ontario | Manufacturers | 68 |
| 8 | oman | maggie | F | 7 | Anglican | Unknown | Ontario | No Occupation Listed | 250 |
| 21 | oman | mary | F | 11 | Anglican | Unknown | Ontario | No Occupation Listed | 250 |
| 24 | oneill | kate | F | 20 | Roman Catholic | Irish | United States | Washing and laundry services | 372 |
| 23 | otoole | elizabeth | F | 18 | Presbyterian | Scottish | Ontario | No Occupation Listed | 217 |
| 22 | otoole | william | M | 21 | Roman Catholic | Irish | Ontario | Cigar makers | 217 |
| 15 | overend | elizabeth | F | 54 | Anglican | English | England | No Occupation Listed | 8 |
| 16 | overend | margaret | F | 28 | Anglican | Irish | England | Governess | 8 |
| 17 | overend | mary | F | 24 | Anglican | Irish | England | No Occupation Listed | 8 |
| 14 | overend | miles | M | 60 | Anglican | Irish | Ireland | Clerk, nfs | 8 |
| 14 | owens | lucy | F | 20 | Roman Catholic | Irish | Ontario | Servants nfs | 253 |