Earth Day is coming and The National Park System is inviting people to celebrate this weekend and admission is free. Admission is free at Muir Woods National Monument in Marin County and San Francisco Maritime National Park in the City. Admission is free at nearly a dozen national parks and monuments in California, including Yosemite, Lassen, Sequoia and Kings Canyon national parks, and Whiskeytown National Recreation Area near Redding. Admission will be free next weekend as well.