The more national parks you visit, the harder it becomes to choose a favorite. So in celebration of National Park month in July, we've chosen the very best in each category. Visit any of these 10 gold-medal parks (or our 10 silver-medal picks) and it's likely you will add these to your own list of favorites.

Great Smoky Mountains National Park in Tennessee and North Carolina

Best mountain park

Great Smoky Mountains National Park,Tennessee/North Carolina. The Great Smoky Mountains are molehills compared to the 10,000-plus-foot peaks in Denali, Rocky Mountain, Mount Rainier, Grand Teton, Yellowstone, Glacier and Haleakala National Parks. But America's largest national park boasts 800 miles of easier-to-hike low-altitude trails and unpaved roads, including 70 miles of the Appalachian Trail. Along with its proximity to the East Coast, this helps make it the most visited of all national parks. The tallest peak is Clingmans Dome, topped by an observation tower on the 6,643-foot summit with panoramic views of the coniferous rainforest.

Silver Medal: Rocky Mountain National Park, Colorado.

Zion National Park in Utah

Best canyon park

Zion National Park, Utah. The multihued canyons of the Southwest are so stunning that nine national parks showcasing their beauty stretch from northern Arizona to southern Utah and Colorado. Grand Canyon is the most famous, but once you've peered into the abyss, there isn't much else to do. There is at Zion, with 18 trails of all difficulty levels, and canyons that are just as “grand." Zion Narrows, for example, which can be explored on foot, is as slim as 20 feet and as tall as 2,000 feet. Viewed at dawn and dusk, Zion's sheer cliffs become rainbows of oranges, reds, purples and tans.

Silver Medal: Grand Canyon National Park, Arizona.

Yellowstone National Park in Wyoming, Montana and Idaho

Best volcanic park

Yellowstone National Park, Wyoming/Montana/Idaho. Geothermal activity is also evident at Hawai'i Volcanoes, Lassen Volcanic and Hot Springs National Parks, but it's hard to beat Yellowstone, America's first national park. It starts with Old Faithful, the world's most famous geyser, which spouts hot-spring water and steam about 140 feet in the air every one to two hours. The park contains half of the world's geysers, plus many “mudpots," steam vents and hot-spring terraces. Add four mountain ranges, wolves, bison, elk and grizzly bears and it's a park erupting with surprises.

Silver Medal: Hawai'i Volcanoes National Park, Hawaii.

Yosemite National Park in California

Best big-rock park

Yosemite National Park, California. Take away the massive granite walls that soar thousands of vertical feet above Yosemite Valley and it would be just another forest —not America's top spot for admiring waterfalls and world-class rock climbers. El Capitan and Half Dome are Yosemite's signature rock faces, while others are bisected by famous waterfalls, like 2,425-foot-high Yosemite Falls and rainbow-swaddled Bridalveil Fall. The park is not all imposing cliffs and thundering falls, though. More than 750 miles of trails snake through Yosemite Valley, up to the falls and in the high country.

Silver Medal: Arches National Park, Utah.

Mammoth Cave National Park in Kentucky

Best caves park

Mammoth Cave National Park, Kentucky. Fifty-five trails are found in this park and dozens of species of fish swim its rivers, but a half-million visitors come each year mostly for what's underneath: the world's largest known network of caves, tunneling more than 400 miles. Designated as a World Heritage Site, these caves can be seen on any of five guided tours, ranging from the fully lit, 75-minute Frozen Niagara Tour to the six-hour Wild Cave Tour that involves serious climbing, squeezing and crawling through muddy and dusty passageways wearing headlamps.

Silver Medal: Carlsbad Caverns National Park, New Mexico.

Isle Royale National Park in Michigan

Best island park

Isle Royale National Park, Michigan. Who would have guessed you could experience the remote island splendor of Lost, minus the scary drama, in Michigan? Isle Royale, a 45-mile-long roadless wilderness, is 56 miles from Michigan's Upper Peninsula in the middle of Lake Superior. Experience all the solitude you can handle on its 165 miles of hiking trails where moose sightings are common, canoe on inland lakes or kayak in the bays (both can be rented on the island). Scheduled ferry service from Houghton, Michigan, operates through September.

Silver Medal: Virgin Islands National Park, U.S. Virgin Islands.

Saguaro National Park in Arizona

Best desert park

Saguaro National Park, Arizona. The mighty saguaro cactus, the symbol of Arizona, is an amazing plant — it can grow up to 60 feet high, live for up to 200 years, store up to 200 gallons of water and serve as a shelter for birds and provide food for animals. At this two-part national park that flanks the western and eastern edges of Tucson, you can learn more about these majestic cacti at the visitor centers and hike in the midst of thousands of them in rolling hills that reach into the mountains.

Silver Medal: Joshua Tree National Park, California.

Kenai Fjords National Park in Alaska

Best glaciers park

Kenai Fjords National Park, Alaska. There are glaciers in other national parks in Alaska, Montana and Washington, but few are as accessible as Exit Glacier near Anchorage. Trails from the parking lot lead you right onto the glacier; President Obama hiked one in 2015 as a way to highlight global warming, which has shortened the glacier by more than a mile. Exit is one of dozens of Harding Icefield glaciers in the park, where you may also spot fjords, whales, moose and bears from your rental car, on a boat tour or on the hiking trail.

Silver Medal: Glacier National Park, Montana.

Acadia National Park, Maine

Best coastal park

Acadia National Park, Maine. Mountain hiking trails, bike-friendly carriage roads and trout-filled ponds occupy the interior of this lone national park in the Northeast, but Acadia is best known for its dramatic rocky coastline. The park is spread out on the Schoodic Peninsula and Mount Desert Island, which is accessible by bridge — plus Isle au Haut and some smaller islands which are accessible by ferry. The coast, most of it easily reached on the park's loop roads or from trails that branch off of them, features cliffs, tide pools, seashell-strewn beaches and a birder's paradise of wetlands.

Silver Medal: Olympic National Park, Washington.

Golden Gate National Recreation Area, San Francisco

Best urban recreation park

Golden Gate National Recreation Area, California. Besides 59 national parks, the National Park Service manages 18 national recreation areas (plus hundreds of national monuments, historical parks and other national treasures). The GGNRA is a sprawling, shore-hugging park in San Francisco and two neighboring counties that includes the Presidio (a former Army base dating to 1776); numerous beaches on the ocean and San Francisco Bay; rugged Coast Range headlands; and recreational opportunities that include some of the best surfing, windsurfing, mountain biking and day hiking in the West — much of it within sight of the Golden Gate Bridge.

Silver Medal: Gateway National Recreation Area, New York/New Jersey.

If you go

United Airlines flies to these airports nearest our top 10 parks: Knoxville (Great Smoky Mountains), St. George (Zion), Cody/YRA (Yellowstone), Fresno (Yosemite), Louisville (Mammoth Cave), Houghton (Isle Royale), Tucson (Saguaro), Anchorage (Kenai Fjords), Bangor (Acadia) and San Francisco (Golden Gate).

Visit united.com or use the United app to plan your national park getaway.