Sections are 1/36th subdivisions of townships, being 1 mile square and legally containing 640 acres of land. In the Land Ordinance of 1785, in which Congress created the PLSS, a methodology for labeling sections was established. Surveyed townships would be subdivided into 36 sections wherein section 1 would be placed in the southeast corner of the township, and section 36 would be placed in the northwest corner (see diagram below). This method of township subdivision was employed in the lands surveyed in southeastern Ohio like the Old Seven Ranges and the Ohio Company Purchase.
The Public Land Act of 1796, modified the method for subdividing townships. Instead of placing section 1 in the southeast corner of the surveyed township, section 1 was now to be placed in the northeast corner. From there, surveyors would number in an alternating east-west pattern, moving southward until section 36 was placed in the southeast corner of the township (see diagram below). This method of section numbering was employed in every cadastral survey west of the Great Miami River in Ohio, and is still standard practice today.
Sections can be further subdivided into aliquot or fractional parts such as half-sections (320 acres), quarter-sections (160 acres), half-quarter sections (80 acres), quarter-quarter sections (40 acres), and fractional or government lots. Note that all of these subdivisions may exist in a single section (see diagram below).