04/09/2012 08:27 am ET Updated Jun 09, 2012

National Park Week Starts April 21

Calling all aspiring Ansel Adamses, budding environmentalists and U.S. travel enthusiasts: National Park Week will be held April 21-29 this year. The parks service is encouraging visitors to "Picture Yourself in a National Park" by waiving entrance fees at all 397 national parks, from the mighty Yosemite in California's stretch of the Sierra Nevada mountains to the tiny Hot Springs National Park in central Arkansas.

The nine-day event starts out with a call to give back. On Saturday, April 21, opportunities abound at Volunteer Day, from battlefield and cemetery cleanups to litter removal along shorelines. And what more fitting place to celebrate Earth Day, on Sunday, April 22, than at some of the most iconic and photographed spots in the country? For the youngest visitors, educational programs to "explore, learn, protect" will be hosted on Saturday, April 28, which will result in the swearing in of the newest crop of official Junior Rangers.

Once you've returned home to your natural habitat, share the photos you've snapped and the new memories made at or on Facebook.

National Park Week is a joint effort of the parks service and the National Park Foundation, the official charity of the national parks, held to promote educational and conscientious visits to America's sacred spots. Pick your park, find a fun activity and definitely don't forget to pack your camera!

Yellowstone National Park
Idaho, Montana and Wyoming: Mountainous terrains, geysers and bears, oh my! Take this chance to see the sights free of cost; entrance fees usually are $25 per car and $12 per person. Unable to make it out West this year? Find solace in the Old Faithful Geyser video webcam.

Grand Canyon National Park
Arizona: Earth Day at the Grand Canyon this year is set to be the largest in the park's history, featuring original interactive exhibits and unique activities, sponsored in part by the Grand Canyon Association, local non-profits and businesses. The free events kick off at the South Rim at 10 a.m. on Sunday, April 22.

Yosemite National Park
California: Take in 1,200 square miles this April, the best time to check out the waterfalls, according to park naturalists. Call ahead or check online to see which hiking trails are open before visiting. Please note: As many parts of the country are warming up, some roads here are still closed due to snow. The entrance fee is regularly $20 per car.

Stones River National Battlefield
Tennessee: With a grant from The History Channel, the Civil War Preservation Trust coordinates a day to clean and tend battlefields across the country. At Stones River, volunteers will be removing modern fencing as well as some invasive plants and trash, on Saturday, April 21.

Saratoga National Historic Park
New York: Earth Day at this Revolutionary War site will be marked over the week by several art shows and exhibits featuring pieces made from recycled and natural materials. Visitors will also be able to scout out the park on a guided bike tour or hear a lecture about climate change.

Sequoia & Kings Canyon National Parks
California: These contiguous parks will be hosting junior ranger activities on the first day of the event, as well as a free three-hour nature walk on Saturday, April 28, along the South Fork Canyon at the South Fork Trailhead in Sequoia National Park.

-- Hilary Solan is an editor at Travelzoo and based in Chicago. Travelzoo has 250 deal experts from around the world who rigorously research, evaluate and test thousands of deals to find those with true value.