Ohio Rev. Code § 157.01
The systems of plane rectangular co-ordinates which have been established by the United States department of commerce for defining and stating the positions or locations of points on the surface of the earth within the state shall be known as the Ohio co-ordinate system of 1927 and the Ohio co-ordinate system of 1983. This chapter applies only to the Ohio co-ordinate system of 1927 and the Ohio co-ordinate system of 1983 and to the use of these systems.
Under these systems the state is divided into a north zone and a south zone.
The area included in the following counties on the effective date of this amendment, shall constitute the north zone: Allen, Ashland, Ashtabula, Auglaize, Carroll, Columbiana, Coshocton, Crawford, Cuyahoga, Defiance, Delaware, Erie, Fulton, Geauga, Hancock, Hardin, Harrison, Henry, Holmes, Huron, Jefferson, Knox, Lake, Logan, Lorain, Lucas, Mahoning, Marion, Medina, Mercer, Morrow, Ottawa, Paulding, Portage, Putnam, Richland, Sandusky, Seneca, Shelby, Stark, Summit, Trumbull, Tuscarawas, Union, Van Wert, Wayne, Williams, Wood, and Wyandot.
The area included in the following counties on the effective date of this amendment, shall constitute the south zone: Adams, Athens, Belmont, Brown, Butler, Champaign, Clark, Clermont, Clinton, Darke, Fairfield, Fayette, Franklin, Gallia, Greene, Guernsey, Hamilton, Highland, Hocking, Jackson, Lawrence, Licking, Madison, Meigs, Miami, Monroe, Montgomery, Morgan, Muskingum, Noble, Perry, Pickaway, Pike, Preble, Ross, Scioto, Vinton, Warren, and Washington.
R.C. §157.01