With fossils present in all states (although New England tends to be fossil poor), you can get a glimpse of the past almost anywhere you backpack. Here are a few places to start. Remember to leave the rocks as you find them; taking fossils from National Park Service land is illegal.
Buffalo River Trail, northern Arkansas. Thirty-seven miles of trail wind along the clear-running Buffalo River. Bluffs and gravel bars make good crinoid and brachiopod fossil-hunting sites. Contact: Buffalo National River, (870) 741-5443; www.nps.gov/buff.
Appalachian Trail, particularly in the Pennsylvania and Virginia sections. Keep an eye out for trilobites, corals, and brachiopods, as well as leaf fossils from plants. For general trail info, contact the Appalachian Trail Conference, (304) 535-6331; www.atconf.org.
Guadalupe Mountains National Park, western Texas. More than 80 miles of rugged trail wind up onto a Permian limestone fossil reef, now the Guadalupe Mountains. Look for sponges and gastropods. Contact: Guadalupe Mountains National Park, (915) 828-3251; www.nps.gov/gumo.
Grand Staircase-Escalante National Monument, southern Utah. This is high-desert canyon country, a prime environment for viewing dinosaur tracks, ammonites, and petrified wood. Contact: Grand Staircase-Escalante National Monument, (435) 644-4300; www.ut.blm.gov/monument.
Borrego Wilderness, Anza-Borrego Desert State Park, southern California. Roam the open desert for sweeping vistas, or navigate 500 miles of infrequently used dirt roads to find ancient oyster shells and camel and mammoth tracks. Contact: Borrego Wilderness, (760) 767-5311; www.anzaborrego.statepark.org.