The system is based on a rectangular grid, with 6x6 mile "townships" made up of 1x1 mile "sections." This forms the basis of the regular pattern visible from the air across most of the country.

Ohio was the first state surveyed using this system, and it's not as regular as the later states, so the townships aren't very square. As you go further west the system becomes more obvious, with streets aligned to the grid, "Baseline" roads (one such road goes through the middle of Boulder, Colorado), and obvious sharp turns at the places where corrections for the curvature of the earth are made.

Each township has one section reserved to support the township's school, and the regular pattern of government-owned sections can also be observed from the air...