Ohio Rev. Code § 1545.15
When conducive to the general welfare, any territory adjacent and contiguous to an existing park district, whether located within or without the county in which such district was created, may be annexed to such district. When a petition is filed with the board of park commissioners requesting such annexation, containing an accurate description of the territory proposed to be annexed, accompanied by an accurate map or plat of such territory, and signed either by a majority of the electors residing within such territory or by not less than fifty such electors, the board shall determine whether it is advisable that such annexation should be made. If the board determines in favor of such annexation, it shall make application to the probate court of the county in which such territory is located, setting forth the fact of the filing of such petition and the reasons why it is advisable that such territory should be annexed to such district. Any such board may of its motion file such petition in such court. Upon the filing of such petition, like proceedings shall be had as are provided in sections 1545.03 and 1545.04 of the Revised Code upon application for the creation of a park district, except that the territory so annexed may include a part only of an existing township or municipal corporation.
R.C. §1545.15