On Wednesday, Warren was 15 miles from the trail's northern end on Mount Katahdin in Maine, the AP reported. However, the teen still has to complete a 100-mile section of the trail that she skipped over earlier in order to reach the mountain before it closes to hikers for winter.
The Appalachian Trail, more commonly known as the AT, stretches more than 2,000 miles from Georgia to Maine. It typically takes about six months to complete, with hikers covering around 15 miles each day.
Warren, who is from Florida, started at the trail's southern end in Georgia on April 1. She celebrated her 15th birthday while passing through Virginia in June.
Warren hikes the trail alone, but her parents are not too far away. They follow her in a camper and can track her whereabouts through a GPS device that posts her location to a website, according to Bangor Daily News.
She meets up with her parents and sleeps in the camper at night when she can, the website writes. Although there have been close to two dozen times when she hasn't ended her day near an access road and has slept on the trail by herself.
Known as "Chipmunk" on the trail, she's been posting updates of her journey to Instagram.
Each year, around 2,000 hikers attempts to travel the AT's full length, but only one-quarter of those make it to the end. Currently, the youngest thru-hiker is a 6-year-old boy who finished the trail with his parents and older sister in 2002, according to the Appalachian Trail Conservancy.