Nearly 331 million people visited the US National Park Service's 417 sites around the United States in 2017, a slight dip from record-breaking number of visits during its centennial anniversary year in 2016.
원문출처 : https://www.cnn.com/travel/article/most-popular-national-park-service-sites-2017/index.html
원문출처 : https://www.cnn.com/travel/article/most-popular-national-park-service-sites-2017/index.html