From FamilySearch Wiki
- Oakfield Plantation (Aroostook Co.) organized from T5 R3 WELS in 1856; incorporated as the Town of Oakfield, Maine in 1897.
- Orangetown Plantation (Washington Co.), aka Number 12 ED Plantation, incorporated as the Town of Whiting, Maine in 1825.
- Orient Plantation (Aroostook Co.)
- Osborn Plantation (Hancock Co.)
- Ossipee Plantation (York Co.)
- Otisfield Plantation (now Oxford Co.) was first organized as a plantation in 1787, and incorporated as the town of Otisfield, Maine in 1798.
- Oxbow Plantation (Aroostook Co.), aka Umcolcus Plantation, was first organized as Number 9 R6 WELS Plantation in 1848; changed name to Oxbow in 1870.
- Oxford Plantation (Oxford Co.)
- Oxford Plantation (Penobscot Co.)
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