Does anyone know where Blackford was? On Plaque out side of courthouse in Mt Vernon, Posey Co, IN POSEY COUNTY HISTORY The first recorded white man to come to Posey County was Tom Jones in 1794. Posey County was named in honor of Thomas Posey, Governor of the Indiana Territory at the time. It was created on Sept 7, 1814. After several changes the present boundry lines were fixed in 1823. The first horse-powered miss was built in 1810 by James Black. The first county seat was Blackford in Jan 1815, and the first court was held in Blackford in Oct. 1816. The county seat was moved to Mt. Vernon in 1825. The seal of Posey County, adopted in 1835, was in honor of William Henry Harrison.... New Harmony was the site of two experiments in communal living, first under Father Rapp, the Harmony Society from 1814 to 1824, and then under Robert Owen from 1825 to 1860.