Residents of Mount Forest, Town—Ville — Sub-district E, surnames O (1881 Census)
| # | Surname | Given | Sex | Age | Religion | Origin | Birthplace | Occupation | HH |
| 18 | obrian | albert | M | 4 | Roman Catholic | American | Ontario | No Occupation Listed | 258 |
| 16 | obrian | johana | F | 30 | Roman Catholic | Irish | Ireland | No Occupation Listed | 258 |
| 15 | obrian | john | M | 37 | Roman Catholic | Irish | United States | Agent nfs | 258 |
| 19 | obrian | john | M | 2 | Roman Catholic | American | Ontario | No Occupation Listed | 258 |
| 20 | obrian | sabina | F | 0 | Roman Catholic | American | Ontario | No Occupation Listed | 258 |
| 17 | obrian | wm | M | 6 | Roman Catholic | American | Ontario | No Occupation Listed | 258 |
| 24 | obrien | edward | M | 76 | Anglican | Irish | Ireland | No Occupation Listed | 195 |
| 13 | oconnell | b | M | 35 | Roman Catholic | Irish | Ireland | Ministers of Religion | 400 |
| 19 | odonahue | angela | F | 1 | Roman Catholic | Irish | Ontario | No Occupation Listed | 153 |
| 15 | odonahue | catherine | F | 12 | Roman Catholic | Irish | United States | No Occupation Listed | 153 |
| 14 | odonahue | ellinor | F | 35 | Roman Catholic | Irish | United States | No Occupation Listed | 153 |
| 16 | odonahue | mable | F | 11 | Roman Catholic | Irish | United States | No Occupation Listed | 153 |
| 17 | odonahue | nellie | F | 7 | Roman Catholic | Irish | United States | No Occupation Listed | 153 |
| 13 | odonahue | patrick | M | 40 | Roman Catholic | Irish | Ireland | Plasterers | 153 |
| 18 | odonahue | ustase | M | 3 | Roman Catholic | Irish | United States | No Occupation Listed | 153 |
| 17 | odonald | barnard | M | 46 | Roman Catholic | Irish | Ireland | Labourers nfs | 401 |
| 23 | odonald | barney | M | 13 | Roman Catholic | Irish | Ontario | No Occupation Listed | 401 |
| 19 | odonald | bridget | F | 19 | Roman Catholic | Irish | Ontario | Servants nfs | 401 |
| 18 | odonald | catherine | F | 42 | Roman Catholic | Irish | Ireland | No Occupation Listed | 401 |
| 24 | odonald | catherine | F | 9 | Roman Catholic | Irish | Ontario | No Occupation Listed | 401 |
| 2 | odonald | johana | F | 5 | Roman Catholic | Irish | Ontario | No Occupation Listed | 401 |
| 21 | odonald | maggie | F | 14 | Roman Catholic | Irish | Ontario | Servants nfs | 401 |
| 25 | odonald | margret | F | 55 | Roman Catholic | Irish | Ireland | No Occupation Listed | 261 |
| 20 | odonald | mary | F | 17 | Roman Catholic | Irish | Ontario | Servants nfs | 401 |
| 1 | odonald | michael | M | 7 | Roman Catholic | Irish | Ontario | No Occupation Listed | 401 |
| 22 | odonald | neil | M | 16 | Roman Catholic | Irish | Ontario | Labourers nfs | 401 |
| 25 | odonald | sarah | F | 8 | Roman Catholic | Irish | Ontario | No Occupation Listed | 401 |
| 14 | oneil | james | M | 0 | Episcopal Methodist | Irish | Ontario | No Occupation Listed | 347 |
| 5 | oneil | jane | F | 63 | Methodist | Irish | Ireland | No Occupation Listed | 362 |
| 12 | oneil | maggie | F | 20 | Episcopal Methodist | Irish | Ontario | No Occupation Listed | 347 |
| 4 | oneil | michael | M | 66 | Methodist | Irish | Ireland | Labourers nfs | 362 |
| 6 | oneil | robert | M | 4 | Methodist | Irish | Ontario | No Occupation Listed | 362 |
| 13 | oneil | saml | M | 1 | Episcopal Methodist | Irish | Ontario | No Occupation Listed | 347 |
| 11 | oneil | wm | M | 22 | Episcopal Methodist | Irish | Ontario | Wood Treaters | 347 |
| 17 | orchard | elizabeth | F | 48 | Methodist | English | England | No Occupation Listed | 214 |
| 16 | orchard | paul | M | 53 | Methodist | English | England | river drivers | 214 |
| 14 | oreilly | francis | M | 28 | Roman Catholic | Irish | Ireland | Ministers of Religion | 400 |
| 25 | orr | annie | F | 47 | Anglican | Irish | Ireland | No Occupation Listed | 31 |
| 4 | orr | jane | F | 30 | Presbyterian | Scottish | Ontario | No Occupation Listed | 398 |
| 2 | orr | john | M | 14 | Anglican | Irish | Ireland | No Occupation Listed | 31 |
| 1 | orr | martha | F | 20 | Anglican | Irish | Ireland | No Occupation Listed | 31 |
| 24 | orr | robert | M | 56 | Anglican | Irish | Ireland | Boot and shoemakers and repairers | 31 |
| 3 | orr | sarah | F | 12 | Anglican | Irish | Ireland | No Occupation Listed | 31 |
| 4 | orr | saul | M | 22 | Anglican | Irish | Ireland | Postal or telegraph clerk nfs | 31 |
| 5 | orr | winnie | F | 5 | Presbyterian | Canadian | Ontario | No Occupation Listed | 398 |
| 3 | orr | wm | M | 34 | Presbyterian | Irish | Ontario | Dealer, merchant etc. (Wholesale & retail trade) | 398 |
| 6 | orr | wm | M | 3 | Presbyterian | Canadian | Ontario | No Occupation Listed | 398 |
| 8 | osborn | charloot | F | 32 | Methodist | Canadian | Ontario | No Occupation Listed | 384 |
| 9 | osborn | george | M | 0 | Methodist | Canadian | Ontario | No Occupation Listed | 384 |
| 7 | osborn | joseph | M | 30 | Methodist | Canadian | Ontario | Farmers, general and nfs | 384 |
| 9 | osullivan | mary | F | 19 | Roman Catholic | Irish | Ireland | Servants nfs | 119 |