Once the exterior boundaries of a township have been run and monumented, the interior is subdivided into thirty-six sections, each nominally one mile square and containing a nominal 640 acres. The order in which that subdivision is executed, and the order in which the resulting sections are numbered, are both fixed by the instructions and both matter in practice.
The numbering is the part everyone remembers, because it is unusual. Section 1 sits in the northeast corner of the township. The numbers run west along the north tier to section 6 in the northwest corner, drop one tier, and run east again from 7 to 12. The alternation continues down the township, ending with section 36 in the southeast corner. This back-and-forth pattern is called boustrophedon, from the Greek for the way an ox turns while ploughing.
The section grid
| Tier | Column 1 (west) | Column 2 | Column 3 | Column 4 | Column 5 | Column 6 (east) |
|---|---|---|---|---|---|---|
| North tier | 6 | 5 | 4 | 3 | 2 | 1 |
| Second tier | 7 | 8 | 9 | 10 | 11 | 12 |
| Third tier | 18 | 17 | 16 | 15 | 14 | 13 |
| Fourth tier | 19 | 20 | 21 | 22 | 23 | 24 |
| Fifth tier | 30 | 29 | 28 | 27 | 26 | 25 |
| South tier | 31 | 32 | 33 | 34 | 35 | 36 |
Several useful facts fall out of the grid immediately. Sections 1 and 36 occupy diagonally opposite corners, northeast and southeast respectively, and sections 6 and 31 the northwest and southwest. Consecutive numbers are always adjacent, sharing a full section line, which is why the sequence is easy to walk. Sections in the same tier differ by at most five. And the sum of a section number and the number directly below it in the adjacent tier is constant within each pair of tiers, which is a quick sanity check when reading a plat upside down in the field.
Why the numbering runs this way
The Land Ordinance of 1785 used a different scheme: sections were numbered from 1 to 36 beginning in the southeast corner and running north up each column. That scheme was used in the earliest Ohio surveys and then abandoned. The Act of May 18, 1796 replaced it with the boustrophedon pattern beginning at the northeast corner, and that has been the rule ever since.
The practical advantage of a serpentine over a column-by-column numbering is continuity of the survey party's route. Because consecutive sections adjoin, a crew running the interior could number and record as it worked without jumping across the township. The choice of the northeast corner as the start is consistent with the order in which the interior lines were actually run.
The order of subdivision on the ground
The numbering and the surveying order are related but not identical. The interior of a township was subdivided by running lines from the south and east boundaries toward the north and west, so that the discrepancy between the record and the ground would accumulate in a known place rather than in an arbitrary one.
- The township exterior boundaries are run and monumented first, with section and quarter-section corners on the exteriors.
- Beginning at the southeast corner of the township, a line is run north 80.00 chains from the section corner on the south boundary, setting the quarter-section corner at 40.00 chains.
- From the section corner so established, a random line is run east to the corresponding corner on the east boundary of the township, the closing error is measured, and the true line is run back west, setting the quarter corner at the midpoint of the true line.
- The process is repeated tier by tier northward through the first range of sections, then range by range westward across the township.
- The last tier of sections on the north and the last range on the west receive whatever measurement remains, so that all excess or deficiency falls in the north and west half-miles.
That last step is the reason a normal township still contains fractional lots along its north and west sides even when no water and no adjoining survey is involved. The system was designed to put its errors somewhere specific, and it chose the north and west.
Sections with special status
Two sections in most townships were set aside rather than sold. Section 16 was reserved for the support of common schools under the earliest legislation, and later grants added section 36, and in some states sections 2 and 32 as well. This is why state trust land in the West appears on maps as a scattered checkerboard rather than in blocks.
- Section 16 lies at the center of the third tier, and section 36 in the southeast corner of the township.
- Where a school section had already been claimed or was fractional, states were granted indemnity or lieu selections elsewhere, which is why the checkerboard is imperfect.
- Sections along the north and west boundaries of a township, numbers 1 to 6, 7, 18, 19, 30 and 31, are the ones most often carrying government lots.
- Section 6, in the northwest corner, is fractional on two sides at once and is normally the most complicated section in a township.
Using the grid in practice
Learning the grid pays for itself quickly. Given a section number you can place it in the township without looking at anything: divide by six to get the tier, and let the remainder tell you the column, remembering that odd-numbered tiers count from the east and even-numbered tiers from the west. Section 14 is in the third tier, which counts from the east, and it is the second column in from the east side.
The grid also makes adjacency checks trivial when reviewing a legal description. If a deed describes land in section 14 and refers to an adjoining tract in section 23, the grid confirms that section 23 lies immediately south of section 14 and the description is plausible. If it referred to section 20, the two are not adjacent and something is wrong in the record.