Hamilton County Chronology

1790, Jan 4 - HAMILTON created by the Northwest Territory from non-county area. (Terr. Papers U.S., 3:294-295; Chase, 3:ch. 331/p. 2096)

1792, Feb 11 - HAMILTON gained from WASHINGTON and from non-county area in the Northwest Territory; HAMILTON included the eastern part of present Michigan. (Terr. Papers U.S., 3:363-364)

1796, Aug 15 - HAMILTON lost to creation of WAYNE (Northwest Territory, extinct); HAMILTON eliminated from present Michigan. (Terr. Papers U.S., 2:567-568 and 3:447; Chase, 3:ch. 332/p. 2096)

1797, Jul 10 - HAMILTON lost to creation of ADAMS. (Terr. Papers U.S., 2:612-613; Chase, 3:ch. 333/p. 2096)

1798, Jun 22 - HAMILTON gained from KNOX (Ind.) in present Indiana and Ohio. (Terr. Papers U.S., 3:509; Chase, 3:ch. 335/p. 2097)

1798, Aug 20 - HAMILTON lost to creation of ROSS. (Terr. Papers U.S., 3:510; Chase, 3:ch. 336/p. 2097)

1798, Sep 1 - HAMILTON lost to ADAMS. (Terr. Papers U.S., 3:510-511; Chase, 3:ch. 337/p. 2097)

1800, Dec 6 - HAMILTON lost to creation of CLERMONT. (Terr. Papers U.S., 3:526; Chase, 3:ch. 339/p. 2097)

1803, Dec 1 - HAMILTON became a county in the state of Ohio. HAMILTON gained from KNOX (Ind.), exchanged with CLARK (Ind.); HAMILTON eliminated from present Indiana. (Ind. Terr., Exec. Journal, 114-115; Pence and Armstrong, 218; U.S. Stat., vol. 2, ch. 40 [1802], secs. 1-3/pp. 173-174; Van Zandt, 112)

1803, May 1 - HAMILTON lost to creation of BUTLER, GREENE, MONTGOMERY, and WARREN. (Ohio Laws 1803, 1st assy., ch. 4, secs. 1-4, 8/pp. 9-12; Chase, 3:ch. 345/pp. 2099-2100)

1808, Jan 20 - HAMILTON lost to BUTLER. (Ohio Laws 1807, 6th assy., ch. 4/p. 10; Chase, 3:ch. 363/p. 2106)

Sources:

The Newberry Library, Atlas of Historical County Boundaries, Chicago, IL. Hamilton County Chronology.