I visited the Appalachian Trail last month, it was incredible!
Oh wow that is a really long trail 2200 miles
Yes I didn't see the whole thing of course.
I hope not that is the longest hiking only trail in the world might take a few years to hike it all. 
I didn't know it was the longest. That's crazy!
Yeah thats why over 2 million people take a hike on a part of it each year
How long has it been a thing?
Its actually not that old is was completed in 1937 after 16 years of development. Alot of improvements and changes continue to this day