CHEYENNE, Wyoming (AP) — Three of America's best-known national parks _ Yellowstone, Grand Teton and Great Smoky Mountains _ closed their gates Tuesday as parks struggle to keep popular recreation areas open while struggling to prevent spreading the coronavirus at congested sites.  They join a growing list of national parks that have closed from New York to California, including the Statue of Liberty and Alcatraz. Rocky Mountain National Park in Colorado and Yosemite National Park in California have also closed. Other parks that remain open have closed shuttles, campgrounds, visitor centers and some trails to prevent the spread of COVID-19.