*Difficulty ratings can be pretty subjective, and may vary by publisher. It's a good idea to pay close attention to elevation gain, length, and trail conditions.
Note: Even if you have a smartphone with GPS technology and downloaded a topographic map, many experts recommend that anyone hiking in the backcountry have a paper topographic map and map-reading and compass skills.
Trail guides, maps, safety, and how-to resources on hiking are published by government agencies that manage public lands, hiking and non-profit groups, individuals, and commercial enterprises. You can find them on the web, in government offices including visitor centers, book and map stores, outfitters, and, of course, libraries. This guide highlights some of my favorite online resources, along with other positively reviewed resources.
The following three sites are good places to begin your research.