Hamilton County (Cincinnati, county seat). Butler County was formed from Hamilton County, which was created by proclamation by Gen. Arthur St. Clair, governor of the Northwest Territory, Jan. 4, 1790. The 1894 Hamilton County history said "the proclamation is dated Jan. 2, but it was not promulgated until the 4th. The former date, however, is generally accepted as the official beginning of its existence." The 1894 history said "John Cleves Symmes, the original purchaser of a large tract of Miami lands, and who had reached the territory in advance of the governor, claimed that he was given the privilege of naming the county, and he chose the name of Hamilton, in honor of Alexander Hamilton, then secretary of the treasury. At the same time Gov. St. Clair gave the village the name of Cincinnati," replacing Losantiville, "which had been invented by John Filson." Hamilton County's original boundaries were: "beginning at the mouth of the Little Miami; thence down the Ohio river to the mouth of the Big Miami [Great Miami River], and up said stream to the Standing Stone Forks; thence in a straight line due east to the Little Miami, then down that stream to the place of beginning." That area covered about an eighth of present Ohio.
The 1894 history said the following counties were created out of the original Hamilton County: Clermont, 1800; Montgomery, 1803; Warren, 1803; Greene, 1803; Butler, 1803; Champaign, 1805; Miami, 1807; Preble, 1808; Darke, 1809; Clinton, 1810. The 1894 history said Hamilton County "is bounded on the east by Clermont [County], south by the Ohio river, the line being low-water mark on the north side, west by Dearborn County, Indiana, and north by Butler and Warren counties. The present area is about 355, square miles, or 227,516 acres.
Sept. 2, 1788, county courts were established and officers appointed at Cincinnati: William Goforth, William Wells and William McMillan, judges of the court of common pleas and justices of the court of general quarter sessions of the peace; Israel Ludlow, clerk of the several courts; and Cincinnati was declared to be the county seat. Other appointments: Jacob Topping, Benjamin Stites and John Stites Gano, justices of the peace; John Brown, sheriff.