The regular rectangular farms that define much of the American Midwest and West are a result of a surveying technique called the township method that the federal government required surveyors to use in the Ohio Territory beginning in 1785.
The township method continued to be used when the Louisiana Purchase was surveyed in the early 1800s.
A township is a square 6 miles (9.7 km) long on each side, oriented to compass directions.
Each township was further divided into 36 one square mile (2.6-sq-km) blocks.
Every so often, the section lines had to bend to allow for the curvature of the Earth.
Later, property lines and often roads followed these rectangles, resulting in a patchwork pattern when viewed from above.
