20 maio 1785 ano - The Northwest Ordinance of 1785, setting the rules for dividing the U.S. Northwest Territory (later Ohio, Indiana, Illinois, Wisconsin and Michigan) into townships of 36 square miles apiece, is passed by the Confederation Congress. Walter G. Robillard and Lane J. Bouman, Clark on Surveying and Boundaries (LexisNexis, 1997) The survey system will later be applied to the continent west of the Mississippi River (Linha do tempo)