( CNN ) From the giant sequoias of Yosemite to the geysers of Yellowstone , the United States ' national parks were made for you and me . And for Saturday and Sunday , they 're also free . Though most of the National Park Service 's 407 sites are free year-round , the 128 parks that charge a fee -- like Yellowstone and Yosemite -- will be free those two days . It 's all part of National Park Week , happening April 18 through April 26 , and it 's hosted by the National Park Service and the National Park Foundation . Check out night-time astronomy parties , daytime Revolutionary War programs , Earth Day parties and family-friendly Junior Ranger activities at national park sites across the country . Not sure how to start ? Go to FindYourPark.com to learn more about park sites near you . Go to www.nationalparkweek.org for more ideas on how to explore . Then the park service wants people to share their stories using the hashtag # FindYourPark and at FindYourPark.com .
It 's fun theme parks , and that year the parks are free ages 18 - 19 . concerts , Revolutionary War programs and other fun happens this week .