Earl Shaffer was a veteran of WWII from Pennsylvania. While serving in WWII his best friend, Walter Winemiller, with whom he planned to hike the AT with, died at Iwo Jima. Though not properly diagnosed, it is reasonable to assume that Shaffer suffered from mental illness that coincided with the end of his service. Upon returning from deployment, Shaffer decided to hike the trail both in memory of Winemiller and to "walk the war out of his system." Ironically, he wrote of all the times he saw violence on the trail: walking past Antietam and that nature itself was violent, like a grouse exploding from underbrush like an A-bomb. He became the first person to thru-hike the trail in a single season. This photo was taken at the end of his NOBO hike on top of Mt.Katahdin in 1948.

A group of backpackers on the Chimney Pond Trail, near Mount Katahdin in Maine, July 1, 1939.

Earl Shaffer at the conclusion of his thru hike of the Appalachian Trail in the summer of 1948. Although some have disputed his claim to have hiked the entire trail that summer, accusing him of skipping sections or hitching rides in cars, Shaffer is still widely considered to be the first "thru hiker" of the Appalachian Trail.

Thru hiker A.J. Matthews (Blue Steel) reaches the end of his thru hike on Mount Katahdin on August 9, 2017.

Mount Katahdin as seen from Daisy Pond (now Daicey Pond), photographed by Myron Avery. This image is from the Myron Avery Scrapbook Collection at the Maine State Library.

Members of a Potomac Appalachian Trail Club (PATC) day hiking group at the summit of Mount Katahdin in 1939. Of the 37 individuals in the image, 22 signed the photograph on the back. Almost half of the group is female, showing the high degree of participation in these expeditions by female members of the Club. It is also worth noting that the now iconic sign on the Katahdin summit was not there in 1939.

Myron Avery and two other hikers on the summit of Mount Katahdin (Maine).