Shortly after America gained it's Independance, the Township and Range System was created for the purpose of surveying newly acquired lands.
Previously Known as the Louisiana Territory, the land purchased from the French comprised of appoximately 529,920,000 acres. In 1803, American Founding Father and U.S. President, Thomas Jefferson, really outdid himself when he closed the most incredible land deal in U.S. history. The United States almost doubled in size from the land gained in the Louisiana Purchase, which resulted in a population increase of around 60,000 new citizens.
Congress had recently created the United States Public Land Survey in 1785, otherwise known as the Township and Range System. This plan called for the systematic partitioning of the land west of the Appalachians into square units known as "townships". Each township was six miles on a side and was subdivided into 36 sections, each one a mile square.
A north-south line called a "principal meridian" and an east-west "baseline" were established for each region of the west as it was settled. Each township was given a township and range number according to how many townships it was away from the intersection of these two lines. The township number tells how many units north or south of the base line it is; the range number how many units east or west of the principal meridian. One baseline and principal meridian may serve an area as large as several states.
There was a problem, however. Since the Earth is round and not flat, it cannot be covered with a regular grid without the squares becoming distorted. Closer to the north pole, the meridians get closer together and the squares are no longer square. To compensate for this, the surveyors had to make corrections to their grid. While attempting to keep each township as close to six miles square as possible, sections along the north and west edges of some townships were distorted to make the grid fit the curve of the Earth. This means that some sections have more or less than 640 acres in them.