Parking, restrooms and park fees are also important to figure out ahead of time. Talk to park rangers to learn about weather and animal hazards along your route. And for longer adventures, don’t forget to bring water and snacks.
“Knowing what to expect when you get out on the trail will help you spend less time during your run worrying about whether you are going the right way and more time enjoying the run,” says Kristen Arendt, editor and content manager for Adventure Projects, an online resource for outdoor aficionados.
Yosemite National Park, CaliforniaYosemite Valley 1 of 7
One of the country's most popular national parks draws some 4 million visitors each year, and Yosemite Valley is a popular stop for tourists.
To escape the crowds, consider the Valley Floor Loop, says Meghan Hicks, a veteran trail runner and senior editor of iRunFar.com.
Wrapping around the perimeter of the valley, the bridle trail is used by hikers, trail runners and horses.
If you're feeling adventurous, you can tackle the full 13-mile loop and check out Yosemite Falls, Merced River and Mirror Lake.
The flat-to-rolling trail is also suitable for runners who don't want to go that far—there are a bunch of ways to shorten it, she says.
Either way, expect to be wowed.
"I've seen deer, bears, and a bobcat along this trail before," she says.
For a more challenging option, Hicks recommends Yosemite Valley's four-mile trail, a grueling 3,200-foot-climb between the valley and Glacier Point.
But the effort will be worth it when you see the stunning sights at the top, she says. The end of the 4.8-mile trail also has restrooms and a refreshment stand.
If you're too exhausted for the descent, you can catch a bus that will take you back to the valley.
Mount Hood National Forest, OregonTrillium Lake 2 of 7
Kylie Brooks/U.S. Forest Service/Mt. Hood National Forest
Though not as famous as the big-name national parks, the Mount Hood National Forest, located about 20 miles east of Portland, is just as stunning.
Trails here provide impressive views of Mount Hood, Oregon's highest mountain at 11,240 feet.
The Trillium Lake Trail—described by the National Forest Service as a "kid-friendly" trail—is a mostly level, two-mile path that circles Trillium Lake with the forest's main attraction as a backdrop.
"When you get on the south side of the lake, you see this enormous volcanic mountain (Mount Hood), and it's always snow-capped," says Richard Bolt, director of online marketing for the American Trail Running Association.
The trail is also located near the Trillium Lake Campground, a popular vacation spot for families.
Olympic National Park, WashingtonHoh River Trail 3 of 7
National Parks Service
With its towering trees, lush vegetation and babbling waters, this enchanting rainforest trail is straight out of a storybook.
The Hoh River Trail is a 17.3-mile path that extends from the Hoh Rainforest Visitors Center to Glacier Meadows and Blue Glacier along Mount Olympus. But you don't have to venture far to get a fulfilling experience.
Starting at the visitors center, run about a mile, and you'll hear and see the steely blue Hoh River, which flows 7,000 feet down from Mount Olympus to the Pacific Ocean.
For the next few miles, soak in the verdant scenery as you pass creeks and cascading waterfalls. The trail's popular turnaround point is Five-Mile Island, a group of gravel bar islands located five miles from the Visitors Center. Elk are known to hang out on its grassy meadows.
Great Smoky Mountains National Park, TennesseeOld Settlers Trail 4 of 7
Jason A G/Flickr
In the Greenbrier section of the Great Smoky Mountains, Old Settlers Trail features fascinating remnants of the past that appeal to runners who love history. The trail is a favorite for Ted Alvarez, Northwest Editor for Backpacker Magazine and author of "The National Parks Coast To Coast: 100 Best Hikes."
"It's a 17-mile point-to-point that rolls up and down over varied terrain, through classic dense Smokies forest and past lots of old historical structures that once belonged to settlers in the park," he says. "The crumbling, hand-made stone walls are especially interesting."
The old homesteads and cemeteries, which date to the late 1800s and early 1900s, have ties to notable Tennessee families, including country singer Dolly Parton.
The trailhead is located on Ramsey Prong Road and travels along Little Pigeon River, seen here.
Shenandoah National Park, VirginiaOld Rag Mountain 5 of 7
National Parks Service
If you want to add climbing to your trail run, Old Rag Mountain is the place to do it.
"Old Rag Mountain in Shenandoah is another major classic," says Alvarez. "Most of it is runnable, and it ends on an exposed, view-filled summit before looping back down to the trailhead. It's also an excellent spot to scope fall colors and wildlife."
The nine-mile trek begins with a gradual two-mile uphill through the woods before you reach the mountain's exposed ridgetop.
"Expect to crawl, climb, shimmy, and scramble through about a mile and a half of boulders, then another half-mile of exposed rock as you approach the summit," according to a National Parks Foundation description.
The climb is a popular park activity, but also one of the most dangerous if you're not prepared, the National Parks Service says.
Acadia National Park, MaineHistoric Carriage Roads 6 of 7
National Parks Service
Acadia—some 35,000 acres of protected wilderness on Maine's Mount Desert Island—offers 45 miles of historic horse carriage roads, which were built by the Rockefeller family.
"Acadia's carriage roads as a whole are terrific for trail running, both because they're wide, gently graded terrain, and because they offer scenic vistas," says Dolores Kong, co-author of acadiaonmymind.com and Falcon hiking guides to Acadia National Park.
One of Kong's favorites is a five-mile route near the Hulls Visitors Center that loops around Witch Hole Pond and Paradise Hill.
It has also attracted some famous tourists.
"President Obama and his family biked this section of the carriage road when they vacationed in Acadia in July 2010," she says.
Gary Allen, race director of the Mount Desert Island Marathon and co-founder of Crow Athletics, recommends a six-mile loop around Eagle Lake, just 1.5 miles from downtown Bar Harbor.
For a more challenging run, he suggests the six-mile South Ridge Trail to the top of Cadillac Mountain, the first place in the U.S. the rising sun reaches each day. The trail starts near Blackwoods Campground.