What is the primary division of townships in terms of size?

The primary division of townships is indeed defined as 1 by 1 square mile. In the Public Land Survey System (PLSS) utilized in the United States, a township is a square tract of land that measures six miles on each side, encompassing a total area of 36 square miles. This township is further subdivided into sections, each measuring 1 mile by 1 mile, resulting in a total of 36 sections per township. This standardization allows for straightforward land division and management, making land transactions easier. Understanding this fundamental size measure is crucial for those involved in real estate and title insurance, as it defines the basic unit of land in many states.