National Park Week is April 17-25. To make it easier to experience America’s Great Outdoors, the National Park Service is waiving entrance fees, so visitors can enjoy all 392 national parks for free starting Saturday April 17th through the Sunday April 25th. Some parks require reservations. In California you can enjoy Alcatraz, Joshua Tree, Santa Monica Mountains and more. You can Camp, hike, bike or simply drive in at no charge.