Each year, only about one out of every four hikers who set out to complete the Appalachian Trail reaches that goal. A thru-hike means traversing nearly 2,200 miles, across 14 states, in a single 12-month period. It’s a monumental feat of physical and emotional endurance. Betty Kellenberger, an 80-year-old retired schoolteacher from Michigan, shares her story of completing the hike.