U.S. National Park Service

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In this photo made available by the National Park Service, JR Kimber receives medical assistance at Congaree National Park in Hopkins, S.C., Tuesday, April 29, 2014. Kimber and his two children were lost in the park for two days. They were rescued and are all in stable condition. (AP Photo/National Park Service)

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This photo provided by the National Park Service, rescue personnel attend to Dakota Kimbler, 10 and his sister Jade Kimbler, 6, after they were lost with their father inside Congaree National Park, Tuesday, April 29, 2014 in Hopking, SC. The family was lost for more than two days in the vast woods and swaps of the park. They are all listed in stable condition. (AP Photo/National Park Service)

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This April 14, 2014 photo released by the National Park Service shows a highway pass on the road in Alaska's Denali National Park and Preserve. In a sure sign of spring, and a perk to those living in Alaska, the only road into Denali National Park and Preserve was opened Friday, April 18 to Mile 30. Officials say weather permitting, the road will remain open to that mile marker until May 20, when tour buses beginning running for the summer. (AP Photo/National Park Service)

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This April 4, 2014 photo released by the National Park Service shows the road going toward the Sable Pass in Alaska's Denali National Park and Preserve. In a sure sign of spring, and a perk to those living in Alaska, the only road into Denali National Park and Preserve was opened Friday, April 18 to Mile 30. Officials say weather permitting, the road will remain open to that mile marker until May 20, when tour buses beginning running for the summer. (AP Photo/National Park Service)

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This March 27, 2014 photo provided by the National Park Service shows P-22 a 4 year old male mountain lion who was recaptured in late March by National Park Service biologists. The mountain lion known to traverse the hills in and around Los Angeles’ largest park has been exposed to rat poison and is suffering from mange. Scientists noticed the big cat known as P-22 was sickly when they recaptured it last month to replace the batteries in its GPS tracking collar. (AP Photo/National Park Service)

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A scrap dealer has brought suit against the National Park Service, claiming the federal government shortchanged him nearly $250,000 for land it purchased for the Flight 93 National Memorial in Pennsylvania. (Associated Press)

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In this Friday, March 7, 2014 photo, Kayci Cook Collins, superintendent of Wupatki National Monument, poses outside her office in Flagstaff, Ariz. The National Park Service, which manages the monument, is at odds with a Navajo family pursuing residency in the vast expanse of grassland and pueblo ruins. (AP Photo/Felicia Fonseca)

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In this March 6, 2014 photo, James Peshlakai, who was born at Wupatki National Monument, poses for a photo at his home in Cameron, Ariz. The National Park Service, which manages the monument, and the Peshlakai family are at odds over the family's pursuit of residency in the vast expanse of grasslands and pueblo ruins. (AP Photo/Felicia Fonseca)