Occoquan, Va. [1 reference]

Ocracoke, N.C. [2 references]

Odelltown, Lower Canada [1 reference]

Ogden, Aaron [1 subentry]

Ogden, Matthias [1 reference]

Ogdensburg, N.Y. [5 references]

Ohio [3 references + 8 subentries]

Ohio County, Va. (now W.Va.) [2 references]

Ohio River [4 references]

Olive Branch (U.S. sloop) [1 reference]

Oneida (U.S. brig) [1 reference]

Oneida County, N.Y. [1 reference]

Oneida Indians [2 references + 2 subentries]

Onís, Luis de [3 references]

Ontario (U.S. schooner) [1 reference]

Ontario County, N.Y. [1 reference]

Orange County, Va. [5 references]

Orange Court House, Va. [4 references]

Oration on the Inauguration of the Federal Constitution… [1 reference]

Orders in council [See redirect]

Oregon Trail [1 reference]

Orleans, Bank of [1 reference]

Orleans County, La. [1 reference]

Orleans Territory [1 reference + 2 subentries]

Orpheus (British frigate) [3 references]

Osgood, Samuel [1 subentry]

Oswego, N.Y. [3 references]

Otis, Harrison Gray [4 references + 1 “see also” entry]

Overton, Walter H. [2 references]