From Ohio History Central
Accurate land descriptions were necessary for the sale of land. The Land Ordinance of 1785, established a federal survey method for dividing public lands into usable sections. This led to a system that uses north-south and east-west lines.<img width="150" alt="map" src="images/naturalHistory/using/meridian.gif" />
For example, the survey of Northwest Ohio used the Ohio-Indiana state line as a line from which to survey. The line was called the "First Principal Meridian." The 41st parallel of north latitude became an intersecting, east-west base line that also was used in surveying.<img width="150" alt="map" src="images/naturalHistory/using/numberedranges.gif" />
Measuring from the meridian (the north-south line) and the base line (the east-west line), surveyors laid out ranges (from east to west of the meridian), and townships (from north to south of the base line). Each "township" consisting of six square miles was divided into 36 "sections" of one square mile each. Surveyors numbered the units of land in order to provide accurate identification of ranges, townships, sections and subdivisions within a section.
Each section contained 640 acres. A section was divided into 160-acre quarter sections.. More surveying divided the quarter sections into farm and town lots.<img width="150" alt="map" src="images/naturalHistory/using/subdividing.gif" />
Congress reserved section 16 near the middle of each township for the use of public schools.