From the blog "TrailGroove Blog"

Among smartphone mapping and GPS apps, Gaia GPS is one of the most popular and one of my favorite smartphone applications for backpacking and hiking. The app is continually updated, and I’ve been using the app for the last 7 years to plan my backcountry trips at home and to plan out days while on the trail. The app has the ability to store what would equate to a huge stack of USGS topos right to my phone for offline use, and is free to download for iOS here, or find it for Android her