- Norwich, New London County, Connecticut, United States1
- Oban, Argyll and Bute, Scotland, United Kingdom1
- Ogdensburg, Franklin Mining District, Sussex County, New Jersey, United States1
- Ohio Drainage1
- Ohio River1
- Onondada Valley, Onondaga County, New York, United States1
- Onondaga County, New York, United States1
- Palermo, Sicily, Italy1
- Palmer Falls, Saratoga County, New York, United States1
- Panama1
- Paraguay1
- Pasco province, Pasco Department, Peru1
- Passamaquoddy Bay, Maine, United States1
- Perkiomen Mines, Perkiomen, Montgomery County, Pennsylvania, United States1
- Perkiomen, Montgomery County, Pennsylvania1
- Perkiomen, Pennsylvania, United States1
- Peterborough, Hillsborough County, New Hampshire, United States1
- Petersburg, Dinwiddie County, Virginia, United States1
- Petersburg, Virginia, United States1
- Philipstown, Putnam County, New York, United States1