24-year-old Katherine Huether moved from her hometown of Somerset, New Jersey to Portland to become a forest ranger.
Last Thursday, she went for a hike in the woods alone, leaving her dog at home and her cell phone in her car.
Oregon TV station KPTV reports the only signs of Huether came when deputies found her car at the trailhead Friday and when searchers found a credit card receipt with her name on it Sunday.
"We are still holding out hope that she'll come back alive and we can hold her again and tell her we love her," said her father, Robert.
Katherine's parents live in Doylestown, Pa., though her father and friends have joined rescue crews in the search effort.
Dozens of professionals and volunteers ventured into the woods near the Bonneville Dam, along a trail where Huether went hiking.
"If anyone can survive 6 days in the outdoors it's Kate Huether," her aunt, Joan Seamon, said.
Three thousand miles away from the search for their niece, Kate's aunts are praying for a phone call with good news from the scene.
Helicopters are searching the treacherous terrain and Kate's friends and relatives have flown out to join search parties.
"They're our only hope right now for them to find her and bring her home," Peggy Sklios said.
Washington authorities do not suspect foul play.
