Kevin Schafer / Oregon Bitter-root (Lewisia rediviva) flowers, Cascade Mountains, Washington

Tim Fitzharris / Cascading river, Rocky Mountain National Park, Colorado

Tim Fitzharris / Cascading river, Rocky Mountain National Park, Colorado

Jeff Foott / Panther Falls, Columbia River Gorge, Washington

Jeff Foott / Panther Falls, Columbia River Gorge, Washington

Michael Durham / Trail through decidous forest, Cascade Head Preserve, Oregon

Tim Fitzharris / Delaware Falls, Ricketts Glen State Park, Pennsylvania

Tim Fitzharris / Ganoga Falls, Ricketts Glen State Park, Pennsylvania

Tim Fitzharris / Dismal Falls, Jefferson National Forest, Virginia

Kevin Schafer / Falls Creek Falls, Gifford Pinchot National Forest, Washington

Kevin Schafer / Wahkeena Falls, Columbia River Gorge, Oregon

Tim Fitzharris / Waterfall, Laurel Creek, Great Smoky Mountains National Park, Tennessee