![](https://www.historynet.com/wp-content/uploads/2019/09/ACWP-191100-MERRILL-04.jpg)
This map of Middle Tennessee is a prime example of the care and intricacy Merrill invested in each of his maps. Lead pencils were used for any data transferred from other maps; corrections were made only with colored pencils. (United States Corps of Engineers/Library of Congress)