National parks have existed in the United States since 1872 when Yellowstone National Park was established. There are now over 400 national park system properties across the country totaling over 84 million acres. In 2016, these parks received over 281 million visitors and had significant positive economic impacts on surrounding communities, generating over $18 billion in local revenue and over 300,000 jobs. However, the future of some national parks is uncertain as the Trump administration has ordered a review of national monuments designated since 1996 with the goal of potentially reducing some of their sizes and protections.