Since its founding in 1916, the National Park Service has been dedicated to the preservation and management of the country’s outstanding natural, historical and recreational resources. Today, the NPS encompasses more than 391 sites across the United States and in Guam, Puerto Rico and the Virgin Islands.
Every year, millions of people visit our beloved national park areas. To meet the needs of visitors and help manage and protect park resources, the NPS hires approximately 10,000 temporary and seasonal employees annually.
http://www.nps.gov/personnel/seasonal.htm