OTSEGO COUNTY, situated in the central part of New York, with Otsego and Canaderaga lakes in the north. Area, 892 square miles. Face of the country, hilly; soil, productive. Seat of justice, Cooperstown. Pop. in 1810, 38,802; in 1820, 44,856; in 1830, 51,372; in 1840, 49,628; in 1850, 48,639.

OSWEGO COUNTY, situated on the northwesterly boundary of New York, with Lake Ontario on the northwest, Oneida lake on the south, and traversed by Oswego river. Area, 923 square miles. Face of the country hilly; soil of middling quality. Seats of justice, Oswego and Pulaski. Pop. in 1820, 13,374; in 1830, 27,104; in 1840, 43,619; in 1850, 62,198.

ORLEANS COUNTY, situated on the northerly boundary of New York, with Lake Ontario on the north, and traversed by the Erie canal. Area, 372 square miles. Face of the country undulating; soil fertile. Seat of justice, Albion. Pop. in 1820, 7,625; in 1830, 17,732; in 1840, 25,127; in 1850, 28,501.

ORANGE COUNTY, situated in the southeast part of New York, with Hudson river on the east, and traversed by the Delaware and Hudson canal. Area, 760 square miles. Face of the country, diversified; soil, productive, and especially adapted to grazing. Seat of justice, Goshen and Newburgh. Pop. in 1810, 24,347; in 1820, 41,213; in 1830, 45,372; in 1840, 50,739; in 1850, 57,145.

ONONDAGA COUNTY, situated in the central part of New York, with Oneida lake on the northeast, and Skeneatelet lake on the southwest, and traversed by Oswego river and the Erie canal. Area, 711 square miles. Face of the country, uneven; soil productive. This county contains the celebrated salt springs of New York, which yield the state an annual revenue of about $171,000. Seat of justice, Syracuse. Pop. in 1810, 25,987; in 1820, 41,467; in 1830, 58,974; in 1840, 67,911; in 1850, 85,991.

ONEIDA COUNTY, situated in the central part of New York, with Oneida lake on the southwest, and traversed by Mohawk river and the Erie canal. Area, 1,101 square miles. Face of the country, diversified; soil productive. Seats of justice, Rome, Utica, and Whittlesborough. Pop. in 1810, 33,792; in 1820, 50,997; in 1830, 71,326; in 1840, 85,310; in 1850, 99,568.

NIAGARA COUNTY, situated at the northwest corner of New York, with Lake Ontario on the north, Niagara river on the west, and Tonawanda creek on the south. Area, 660 square miles. Face of the country, undulating and hilly; soil, productive. Seat of justice, Lockport. Pop. in 1810, 8,971; in 1820, 22,990; in 1830, 18,485; in 1840, 31,132; in 1850, 42,260.

NEW YORK COUNTY, is situated at the southeast part of the state, between Hudson and East rivers, and includes Manhattan. Blackwell's, Ward's, and Randall’s islands. Area, 20 square miles. Face of the country, undulating; soil, fertile. Seat of justice, New York city. Pop. in 1653, 1,129; in 1661, 1,743; in 1675, 2,580; in 1696, 4,455; in 1730, 8,256; in 1756, 10,530; in 1774, 22,861; in 1786, 23,688; in 1790, 33,131; in 1800, 60,489; in 1810 96,373; in 1820, 123,706; in 1830, 202,569; in 1840, 312,710; in 1850, 515,507.

MONTGOMERY COUNTY situated toward the east part of New York, and traversed by Mohawk river and the Erie canal. Area, 356 square miles. Face of the country diversified; soil rich, except where rocky. Seat of justice, Fonda. Pop. in 1810, 41,214; in 1820, 37,569; in 1830, 43,595; in 1840, 35,818; in 1850, 31,992.