Residents of Markham — Sub-district C, surnames O (1881 Census)
| # | Surname | Given | Sex | Age | Religion | Origin | Birthplace | Occupation | HH |
| 11 | obrien | bridget | F | 22 | Roman Catholic | Irish | Ontario | No Occupation Listed | 230 |
| 12 | obrien | daniel | M | 19 | Roman Catholic | Irish | Ontario | Farmers, general and nfs | 230 |
| 9 | obrien | ellen | F | 58 | Roman Catholic | Irish | Ireland | No Occupation Listed | 230 |
| 14 | obrien | ellen | F | 16 | Roman Catholic | Irish | Ontario | No Occupation Listed | 230 |
| 13 | obrien | john | M | 18 | Roman Catholic | Irish | Ontario | Farmers, general and nfs | 230 |
| 10 | obrien | margart | F | 28 | Roman Catholic | Irish | Ontario | No Occupation Listed | 230 |
| 8 | obrien | timoth | M | 30 | Roman Catholic | Irish | Ireland | Farmers, general and nfs | 230 |
| 14 | ogg | anna | F | 0 | Presbyterian | Scottish | Ontario | No Occupation Listed | 196 |
| 12 | ogg | maria | F | 26 | Presbyterian | German | Ontario | No Occupation Listed | 196 |
| 11 | ogg | william | M | 25 | Presbyterian | Scottish | Scotland | Labourers nfs | 196 |
| 13 | ogg | william | M | 2 | Presbyterian | Scottish | Ontario | No Occupation Listed | 196 |
| 9 | oneill | isaac | M | 49 | Presbyterian | Irish | Ontario | Brick and tile makers | 60 |
| 21 | oneill | marhsal | M | 25 | Methodist | Irish | Ontario | Labourers nfs | 182 |
| 10 | oneill | mary | F | 30 | Baptist | English | Ontario | No Occupation Listed | 60 |
| 22 | oneill | mary | F | | Methodist | English | England | No Occupation Listed | 182 |
| 5 | oster | albert | M | 14 | Presbyterian | German | Ontario | No Occupation Listed | 117 |
| 6 | oster | franklin | M | 12 | Presbyterian | German | Ontario | No Occupation Listed | 117 |
| 3 | oster | john | M | 42 | Lutheran | German | Ontario | Labourers nfs | 117 |
| 7 | oster | maggie | F | 9 | Presbyterian | German | Ontario | No Occupation Listed | 117 |
| 4 | oster | matilda | F | 42 | Presbyterian | Irish | Ontario | No Occupation Listed | 117 |
| 10 | ostertog | alexander | M | 7 | Presbyterian | Scottish | Ontario | No Occupation Listed | 134 |
| 11 | ostertog | arthur | M | 4 | Presbyterian | Scottish | Ontario | No Occupation Listed | 134 |
| 12 | ostertog | george | M | 2 | Presbyterian | Scottish | Ontario | No Occupation Listed | 134 |
| 7 | ostertog | janet | F | 18 | Presbyterian | Scottish | Ontario | No Occupation Listed | 134 |
| 4 | ostertog | jemima | F | 25 | Methodist | English | Ontario | No Occupation Listed | 133 |
| 3 | ostertog | joseph | M | 23 | Methodist | German | Ontario | Farmers, general and nfs | 133 |
| 6 | ostertog | mary | F | 43 | Presbyterian | English | Ontario | No Occupation Listed | 134 |
| 9 | ostertog | robert | M | 13 | Presbyterian | Scottish | Ontario | No Occupation Listed | 134 |
| 8 | ostertog | thomas | M | 15 | Presbyterian | Scottish | Ontario | No Occupation Listed | 134 |