Platmap divided into sections. enlarge

Early Surveys of the United States
Many of the land surveys conducted in the original thirteen colonies were not standardized. These early surveys included little information on vegetation or other natural features. The need for a more systematic and reliable land survey grew with westward expansion following the Revolutionary War. The federal government needed a way to parcel out and describe the location of lands for sale to settlers. The settlers needed to be able to locate and document their claims accurately.

New Legislation
In 1785, the Continental Congress of the United States established the General Land Office through which land was sold, and the Office of the Surveyor General, which was responsible for surveying the land. A commission devised a new plan for locating, describing, and parceling out lands. Thomas Jefferson was a member of the commission that prepared this plan. The plan stipulated that lands be surveyed prior to settlement and that the surveys be conducted in a consistent and standardized manner. 

Townships
In 1786 another act of Congress directed that territory be surveyed into townships, six miles square, which were bounded by lines running true north and south, and east and west. Each township was to be divided into 36 sections, one square mile each, by lines running north, south, east and west. The sections were numbered from one to thirty-six. Instructions to surveyors directed them to describe vegetation and the general character of the land they surveyed in greater detail.

Illinois Surveys
The land survey of Illinois began in 1804 at the southern tip of the state. It worked its way north and was finished in 1855. Land surveys in Illinois involved surveying forest and prairies. Trees played an important part in surveying.