The Pacific Crest Trail (PCT) is roughly 2650 miles and passes through only three states as it makes its way from the Mexico border to the Canada border through California, Oregon, and Washington. Nearly 65% of the trail (1700 miles) is in California alone.
The trail was deemed completed in 1993, despite being one of the two original trails named in the National Trails System Act of 1968. The first reported through hike was in 1970 by Eric Ryback, who hiked the Appalachian Trail in 1969 and the route of what was to become the Continental Divide Trail in 1972. These three trails are collectively known as the ‘Triple Crown’ of hiking.
While the trail itself is maintained by public entities (National Park Service and US Forest Service), the trail is supported by the Pacific Crest Trail Association (PCTA).
Cheryl Strayed published the first popular book, Wild: From Lost to Found on the Pacific Crest Trial, about her hiking sections of the PCT from the Mojave desert to the Columbia river in 2012 and a movie released in 2014. Prior to 2010, fewer than 150 people reported completing the PCT in any given year. That number was around 450 per year in 2013 and 2014, and over 650 in 2015.
The PCTA issues permits for hiking more than 500 miles of the PCT in one trip and issued 4453 permits in 2015 for the 652 reported completions. So fewer than 15% of hikers who set out to hike more than 500 miles of the trail actually complete it.
View a listing of 2600 milers and statistics about completions over the years: http://www.pcta.org/our-work/trail-and-land-management/pct-visitor-use-statistics/
Read more about the PCT from Wikipedia: https://en.wikipedia.org/wiki/Pacific_Crest_Trail