Expert Tips on Lesser-Known National Parks Steer Clear of Crowds Click on the slideshow to see what you're missing in the uncrowded parks recommended by our experts. Visitor statistics are for 1997, as recorded by the National Park Service. (Randy Ramsey/ABCNEWS.com)

    And the gates are closed.
     It happens. Several times over the last few years, for instance, park workers

Yellowstone can fill up in summer, and five parks drew even more visitors last year. (PNI)

have had to close the gates for up to six hours to relieve congestion on the road through Yosemite Valley. While California's well-known park is the most overcrowded, it's not the only one that's overrun.
     Park official Christine Caldes says Yosemite simply can't handle the five to six thousand carloads of folks that show up on a busy summer weekend. "We could accommodate everybody if we paved the entire valley," she says, "but that would probably hurt the visitor experience."

Top 10 Trouble Spots
The busy parks are working to ameliorate some of their overcrowding problems. Yosemite is running buses along the valley road and eventually will close certain roads to cars. Meanwhile, though, your best option for avoiding gridlock among the flora and fauna is to steer clear of the most popular parks during summer's high season.
     Here are the 10 parks that the National Park Service says had the most visitors in 1997:

The 10 Most Popular Parks

1. Great Smoky Mountains, TN/NC (9.96 million)

2. Grand Canyon, AZ (4.79 million)

3. Olympic, WA (3.85 million)

4. Yosemite, CA (3.67 million)

5. Rocky Mountain, CO (2.96 million)

6. Yellowstone, WY/MT (2.89 million)

7. Acadia, ME (2.76 million)

8. Grand Teton, WY (2.66 million)

9. Zion, UT (2.45 million)

10. Mammoth Cave, KY (2 million)

Hot Tips on Where the Crowds Aren't
But don't worry—there are other options besides your backyard. The National Park Service administers a whopping 376 federal properties, including not just national parks but national monuments, recreation areas, historical parks, seashores, lakeshores, battlefields, memorials and rivers.
     If you're content to leave the most famous parks for the off-season, there are plenty of others where you can put together an awesome summer trip, no matter what you're into. We got in touch with three guys who really know what's off the beaten path: Tom Shealey, editor of Backpacker magazine; Craig Allin, editor of International Handbook of National Parks and Nature Reserves; and Dwight T. Pitcaithley, chief historian of the National Park Service.
     These three experts offered their recommendations on where to go to get away (see the map above) and how to make the most of your visits.
     They all echoed the same refrain about crowds in the parks: If you're willing to get out of the car and walk, you'll be out of the fray after about five minutes on the trail.
     Make sure you have some water and a first-aid kit stashed somewhere in your daypack, and just break away. Park rangers are a great source of information, and if you ask nicely, they'll probably point you to fun, uncrowded trails.
     A final note: There are many more parks that aren't packed with people. Some parks in the Southwest didn't make our list above because they are unpleasantly hot in summer. For more tips, talk to fellow travelers, orient yourself on the Web, or read what other park-goers wrote in our chatroom (see links at left).