Hamilton County, Ohio
Hamilton County is located in the southwestern corner of the U.S. state of Ohio. As of the 2020 census, the population was 830,639,[2] making it the third-most populous county in Ohio. The county seat and largest city is Cincinnati.[3] The county is named for the first Secretary of the Treasury, Alexander Hamilton.[4] Hamilton County is part of the Cincinnati-Middletown, OH-KY-IN Metropolitan Statistical Area.
Not to be confused with Hamilton, Ohio.
Hamilton County
United States
January 2, 1790[1]
Cincinnati
413 sq mi (1,070 km2)
406 sq mi (1,050 km2)
6.7 sq mi (17 km2) 1.6%
830,639
825,037 
2,045.91/sq mi (789.93/km2)
History[edit]
The southern portion of Hamilton County was originally owned and surveyed by John Cleves Symmes, and the region was a part of the Symmes Purchase. The first settlers rafted down the Ohio River in 1788 following the American Revolutionary War. They established the towns of Losantiville (later Cincinnati), North Bend, and Columbia.
Hamilton County was organized in 1790 by order of Arthur St. Clair, governor of the Northwest Territory, as the second county in the Northwest Territory. Cincinnati was named as the seat. Residents named the county in honor of Alexander Hamilton, who was the first Secretary of the Treasury of the United States and a founder of the Federalist Party. Its original boundaries were those defined for the Symmes purchase contract in 1788:[5] the Ohio River in the South, Great Miami River to the west, the Lesser Miami River to the east, and the Cuyahoga River to the North. Its area then included about one-eighth of Ohio and had about 2,000 inhabitants (not including the remaining Native Americans).
The county was greatly expanded in 1792 to include what is today the lower peninsula of Michigan. Since 1796, other counties were created from Hamilton, reducing the county to its present size. The county was the location of much of the Northwest Indian War before and after its organization.
The United States forcibly removed most of the Shawnee and other Indian peoples to move to locations west of the Mississippi River in the 1820s.
Rapid growth occurred during the 1830s and 1840s as the area attracted many German and Irish immigrants, especially after the Great Famine in Ireland and the revolutions in Germany in 1848.
During the Civil War, Morgan's Raid (a Confederate cavalry campaign from Kentucky) passed through the northern part of the county during the summer of 1863.
The Sharonville Engineer Depot was constructed by the United States Army in northern Hamilton County in 1942, and continued to be used by the General Services Administration and then the Defense Logistics Agency after 1949. It is currently mostly redeveloped for industrial purposes.