Residents of Innisfil — Sub-district H, surnames O (1881 Census)
| # | Surname | Given | Sex | Age | Religion | Origin | Birthplace | Occupation | HH |
| 24 | obrien | agnes | F | 20 | Roman Catholic | Irish | Ontario | Dressmakers | 40 |
| 22 | obrien | annie | F | 26 | Roman Catholic | Irish | Ontario | Tailors and tailoresses | 40 |
| 23 | obrien | bridget | F | 22 | Roman Catholic | Irish | Ontario | No Occupation Listed | 40 |
| 4 | obrien | catherine | F | 9 | Roman Catholic | Irish | Ontario | No Occupation Listed | 40 |
| 21 | obrien | james | M | 27 | Roman Catholic | Irish | Ontario | Farmers, general and nfs | 40 |
| 3 | obrien | john | M | 11 | Roman Catholic | Irish | Ontario | No Occupation Listed | 40 |
| 2 | obrien | louisa | F | 13 | Roman Catholic | Irish | Ontario | No Occupation Listed | 40 |
| 1 | obrien | margaret | F | 15 | Roman Catholic | Irish | Ontario | No Occupation Listed | 40 |
| 25 | obrien | mary | F | 17 | Roman Catholic | Irish | Ontario | No Occupation Listed | 40 |
| 5 | obrien | mary | F | 51 | Roman Catholic | Irish | Ireland | No Occupation Listed | 40 |
| 20 | obrien | michael | M | 29 | Roman Catholic | Irish | Ontario | Farmers, general and nfs | 40 |
| 1 | oconnell | hanorah | F | 30 | Roman Catholic | Irish | Ontario | No Occupation Listed | 126 |
| 15 | oconnell | margaret | F | 41 | Roman Catholic | Irish | Ireland | No Occupation Listed | 129 |
| 25 | oconnell | mary | F | | Roman Catholic | Irish | Ireland | No Occupation Listed | 126 |
| 2 | oconnell | michael | M | 28 | Roman Catholic | Irish | Ontario | Farmers, general and nfs | 126 |
| 14 | oconnell | timothy | M | 40 | Roman Catholic | Irish | Ireland | Farmers, general and nfs | 129 |
| 7 | oconnor | ellen | F | 14 | Presbyterian | Irish | Ontario | Servants nfs | 198 |
| 19 | oconnor | ellen | F | 15 | Anglican | Irish | Ontario | No Occupation Listed | 107 |
| 23 | odriscall | mary | F | 24 | Methodist | Irish | Ireland | No Occupation Listed | 15 |
| 20 | oharow | mary | F | 36 | Roman Catholic | Irish | Ireland | No Occupation Listed | 237 |
| 17 | oliver | jessie | F | 58 | Anglican | English | England | No Occupation Listed | 103 |
| 18 | olsen | annetta | F | 42 | Lutheran | Norwegian | Norway | No Occupation Listed | 186 |
| 19 | olsen | nekaline | F | 6 | Lutheran | Swedish | Ontario | No Occupation Listed | 186 |
| 24 | orchard | alice | F | 20 | Methodist | English | Ontario | No Occupation Listed | 193 |
| 1 | orchard | bertha | F | 17 | Methodist | English | Ontario | No Occupation Listed | 193 |
| 25 | orchard | elizabeth | F | 19 | Methodist | English | Ontario | No Occupation Listed | 193 |
| 18 | orchard | frances | F | 50 | Methodist | Irish | Ireland | No Occupation Listed | 186 |
| 2 | orchard | harriet | F | 15 | Methodist | English | Ontario | No Occupation Listed | 193 |
| 20 | orchard | joseph | M | 17 | Methodist | Irish | Ontario | No Occupation Listed | 186 |
| 23 | orchard | levinia | F | 22 | Methodist | English | Ontario | No Occupation Listed | 193 |
| 21 | orchard | mime | F | 13 | Methodist | Irish | Ontario | No Occupation Listed | 186 |
| 19 | orchard | orlander | F | 20 | Methodist | Irish | Ontario | No Occupation Listed | 186 |
| 22 | orchard | sarah | F | 50 | Methodist | English | Ontario | No Occupation Listed | 193 |
| 11 | orr | bella | F | 25 | Presbyterian | Irish | Ireland | No Occupation Listed | 195 |
| 12 | orr | eliza | F | 18 | Presbyterian | Irish | Ireland | No Occupation Listed | 195 |
| 10 | orr | margaret | F | 65 | Presbyterian | Irish | Ireland | No Occupation Listed | 195 |
| 6 | orr | thos | M | 22 | Reformed Presbyterian | Irish | Ireland | Farmers, general and nfs | 55 |