How did the states establish long straight borders before GPS?

[Dave Monroe]

How did the states establish long straight borders before GPS?
November 13, 2009
Dear Cecil:

How is it that, in places without natural features such as a river or
mountain range to mark a border, U.S. states could establish a nice,
even line over hundreds of miles before GPS?

— Granite-Morale

Cecil replies:

[...]

http://www.straightdope.com/columns/read/2907/how-did-the-states-establish-long-straight-borders-before-gps