Ohio Rev. Code § 5559.01
Whenever any territory outside the limits of a municipal corporation having a planning commission or a platting commissioner, and within three miles of the corporate limits of such municipal corporation, has been platted into building lots and the plan of the streets approved by such commission or commissioner, and the plat of such addition has been regularly filed in the office of the county recorder, all streets in the newly platted territory shall be under the control and supervision of the board of county commissioners. The board may expend each year on the maintenance of the streets in such territory, until such time as the streets have been permanently improved or the territory has become a part of a municipal corporation, a sum equal to not more than fifty per cent of the moneys levied or collected during the year as taxes from such territory, for road or highway purposes.
R.C. §5559.01