View images of tourists exploring National Parks across the country. As the United States grew and its population expanded and settled westward, regions of the country that displayed natural beauty and ecological diversity became a source of pride. An idea formed that these areas should be maintained and protected for all to enjoy as part of the country’s heritage. This idea would develop into the National Park System over the next 150 years. America’s National Parks draw as many as 330 million visitors every year who are drawn to the unique beauty, geographic, and ecological diversity on display.