Constitution of the State of Ohio Art. II, § 30

No new county shall contain less than four hundred square miles of territory, nor, shall any county be reduced below that amount; and all laws creating new counties, changing county lines, or removing county seats, shall, before taking effect, be submitted to the electors of the several counties to be affected thereby, at the next general election after the passage thereof, and be adopted by a majority of all the electors voting at such election, in each of said counties; but any county now or hereafter containing one hundred thousand inhabitants, may be divided, whenever a majority of the voters, residing in each of the proposed divisions, shall approve of the law passed for that purpose; but, no town or city within the same, shall be divided, nor, shall either of the divisions contain less than twenty thousand inhabitants.