Residents of Brockville, West Ward—Quartier — Sub-district A, surnames O (1881 Census)
| # | Surname | Given | Sex | Age | Religion | Origin | Birthplace | Occupation | HH |
| 18 | obrien | james | M | 20 | Roman Catholic | Irish | Ontario | Machinists | 192 |
| 2 | obrien | james | M | 7 | Roman Catholic | Irish | Ontario | No Occupation Listed | 261 |
| 19 | obrien | john | M | 13 | Roman Catholic | Irish | Ontario | Labourers nfs | 192 |
| 25 | obrien | john | M | 31 | Roman Catholic | Irish | Ontario | Stationary engineers and engine men | 261 |
| 17 | obrien | mary | F | 21 | Roman Catholic | Irish | Ontario | Factory labourers (non-specified manufacturing) | 192 |
| 1 | obrien | mary | F | 30 | Roman Catholic | Irish | Ontario | No Occupation Listed | 261 |
| 15 | oconner | martin | M | 65 | Roman Catholic | Irish | Ireland | Drivers (general haulage) | 206 |
| 16 | oconner | mary | F | 60 | Roman Catholic | Irish | Ireland | No Occupation Listed | 206 |
| 17 | oconner | mary | F | 22 | Roman Catholic | Irish | Ontario | Teachers (unspecified) | 206 |
| 5 | oleary | maggie | F | 24 | Anglican | English | Ontario | Servants nfs | 367 |
| 13 | osier | clinton | M | 6 | Methodist | Scottish | Ontario | No Occupation Listed | 112 |
| 12 | osier | lizzie | F | 25 | Methodist | Scottish | Ontario | Servants nfs | 112 |