O'Brien, Lewis M. [1 subentry]

O'Brien, Richard [8 subentries]

Ocean, L' (French ship) [1 reference]

Ogden, John Cosen [1 subentry]

O'Hara, Charles [1 subentry]

Ohio Gazette, and the Territorial and Virginia Herald (Marietta) [1 reference]

Ohio River [4 references]

Ohio Territory [4 references]

Oldenburg, duke of [See redirect]

Oldenburg, Germany [1 subentry]

Oliver, John [1 reference]

Oliver, Robert [1 reference]

Olney, Jeremiah [1 reference + 1 subentry]

Olson [See redirect]

Ontario County, N.Y. [1 reference]

Oran, Algiers [1 reference]

Orange (U.S. schooner) [1 reference]

Orange County, Va. [4 references]

Orange Court House, Va. [2 references]

Oribe y Vargas, P. [1 subentry]

Orion (U.S. ship) [1 reference]

Orlando (U.S. ship) [3 references]

Orr, Benjamin Grayson [4 references + 1 “see also” entry]

Osgood, Samuel [2 references]

Ostend, Belgium [3 references]

Oswego (U.S. ship) [2 references]

Otis, Harrison Gray [2 references]

Otis, Sally Foster (Mrs. Harrison Gray) [1 reference]

Ottman, Sidi Mohamet ben [1 subentry]

Otto, Louis-Guillaume [2 subentries]

Ottoman Empire [See redirect]