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Our first and foremost national park, Yellowstone was established in 1872 by Congress. Today, it encompasses 2.2-million acres and draws over 3-million visitors yearly. But it's under constant threat from pollution, urban encroachment, and the same tourists that have made it so valuable . We join ecologists, as well as the National Parks Service, in their search for ways to preserve this vitally important ecosystem, while keeping it available to visitors for years to come.