- before 1788 - see the descriptions and links on the Ontario GenWeb site for Frontenac County
- 1788 - 1849 - the area was called Mecklenburg District, then Midland District. Learn more on the Archives of Ontario website.
- 1849 - 1998 - Frontenac County was comprised of eighteen townships, of which Oso Township was one.
- 1998 - present - Oso Township was amalgamated into the Township of Central Frontenac in Frontenac County.
Towns and Villages
- Clarendon Station
- Crow Lake
- Lillies Mill
- Oso Station
- Sharbot Lake * (KFPL Library Branch)
- St. George's Lake