To celebrate the 100th anniversary of the U.S.'s National Parks Service, REI has formed a partnership with the National Parks Service and has pledged millions of dollars to create park guides, digital content, live coverage, and an app, the REI Co-op Guide to the National Parks.

The app contains trail maps, history, and descriptions for several national parks along with information shared by users.

In a statement, REI said that the app is "powered by the collective knowledge of the outdoor community and puts their shared wisdom about deeper park experiences into the hands of America's adventurers," according to the Seattle Times.

The app is free, and perfect for anyone who hears the call of adventure and wishes to explore the seldom-visited nooks of the National Parks.

Available for iOS and Android, the app was developed by Adventure Projects, a Colorado tech firm that REI acquired last June for an undisclosed sum. The company also runs five websites that provide guides and community forums for various outdoor sports including rock climbing, hiking, trail running, and mountain biking.

REI intends to map "every single trail in every National Park" in the U.S., according to Gear Junkie. Seven major parks are available at the moment, and REI says it has been adding hundreds of miles of trails on a monthly basis.

The US National Park Service turns 100 on Aug. 25, 2016 and has been preparing a series of events and programs to commemorate the event. The NPS posted on their website, saying, "We want people everywhere to embrace the opportunities to explore, learn, be inspired or simply have fun in their 407 national parks, as well as understand how the National Park Service's community-based recreation, conservation, and historic preservation programs positively impact their own communities."