To read a township map of Ohio, examine the 36-section grid that is laid over the map; this grid typically measures six miles on each side. The north-south line running through the center of the square is called the Principal Meridian. The east-west line through the center is called the base line. Each of the smaller squares in the grid measure one square mile, or 640 acres.
Sections are numbered in rows, starting with the northeast corner; for example, the top row of squares is numbered 6 through 1 if you read them from left to right. The second row is labeled 7 through 12, the third 18 through 13, and so on. These section blocks are divided into smaller parcels that are labeled according to compass points. For example, the northern half of a section block equals 320 acres, and the southeast quarter equals 160 acres. If you are searching a township map for the northern half of the southwest quarter, you are looking for an 80-acre parcel.
The tier and range numbers are located at the top of township maps and identify the particular area of land the map depicts. Names and dates may also be printed at the top of older maps, although this is not true in all cases.
The U.S. Department of the Interior's Bureau of Land Management oversees the Public Land Survey System that creates township maps. This system is used to map and subdivide all parcels of public land in the United States. Over the years, some public land has been transferred to private ownership, while some private lands have entered the public domain. However, all township maps use the Public Land Survey System.