Miami County, OH adjoins Shelby near Troy metropolitan centre granting a 2020 estimated population standing at 104,273 making it the 11th highest populous county located within Ohio overall. Its county seat is Troy with other cities include Tipp City & Piqua-Troy itself equates out to Miami's largestcity aside from noted country seat. This area had been formed out of Clark and Darke Counties back in 1807 when local citizens petitioned for new administrative boundaries - posthumously named after Native American Tribe Miami stewardship during era Thomas Jefferson .