From the website:
American Hiking Society’s signature trail awareness program, National Trails Day® (NTD), inspires the public and trail enthusiasts nationwide to seek out their favorite trails to discover, learn about, and celebrate trails while participating in educational exhibits, trail dedications, gear demonstrations, instructional workshops and trail work projects.
NTD also provides an opportunity to thank volunteers, land managing agencies, and outdoor-minded businesses for their support in developing and maintaining trails. Click here for more information.
Check the NTD site for state specific information and details on where events are happening near you.