What are base lines in the context of the US Survey System?

In the context of the US Survey System, base lines are indeed lines that run from east to west and follow latitudes. These lines serve as fundamental references for the establishment of land surveys, allowing for a systematic method of mapping and dividing land across the country.

Base lines are crucial because they work in conjunction with principal meridians, which are vertical lines running north to south. Together, they create a grid system that enables surveyors to define land parcels accurately. Each township in the Public Land Survey System is created by the intersection of a base line and a principal meridian, facilitating the organization of land for ownership and development.

This systematic approach was designed to ease land distribution and make it easier to reference land ownership within a defined geographical space, especially as territories were developed and settled.