What is the legal unit of length used for surveying public lands in the U.S.?

The legal unit of length used for surveying public lands in the U.S. is the chain. A chain is a specific measurement equal to 66 feet, and it was widely used in land surveying, particularly during the 19th century when the rectangular survey system was developed. In this context, the chain serves as a standard unit for measuring areas and establishing boundaries in the Public Land Survey System.

This measurement was adopted for its practicality, as it conveniently divides into larger and smaller units, facilitating various calculations and making it easier for surveyors to lay out plots of land. The chain is still referenced today in surveying practices, particularly in relation to historical surveys and legal land descriptions.

The other options, while they are units of measure, do not serve as the standard unit of length for surveying public lands. The foot and rod are also used in surveying; however, they do not carry the same legal significance specifically in terms of public land surveys. The mile is a larger measurement not typically employed in the day-to-day work of surveying public land parcels.