Question: What was the last place to be mapped in the contiguous U.S.?
Answer: The Grand Staircase-Escalante National Monument in southern Utah, a geologic labyrinth of uncharted canyons that remains one of the most treacherous and inaccessible places in America. It was the last place to be explored in the U.S. in the 1870s and is extraordinary in its topology. The link above has photos.
