Alfred Beilhartz, who was four years old when he went missing, disappeared on July 3, 1938. According to Strange Outdoors, Beilhartz’s family had been camping at Colorado’s Rocky Mountain National Park, close to the Fall River Lodge. Beilhartz had followed his father to the stream to wash up, and then he went to family friends 500 feet upstream. Once everyone had returned to camp, they noticed Beilhartz had gone missing.

Given how little time had elapsed, they were sure Beilhartz could not have gotten far. Park rangers soon rallied 100 members of the Civilian Conservation Corps, but even the Bloodhounds they brought could not pick up Beilhartz’s scent. According to The Charley Project, the rangers dammed the river in case he drowned but still turned up nothing. The search was called off after ten fruitless days.

A couple claimed to have seen Beilhartz atop a rocky outcrop called Devil’s Nest, six miles and around 3,000 feet higher from where he had gone missing. The child made a “shrill noise” over the edge and then left or was pulled back. Another woman thought that she had seen him with an unknown man on the road.

The family received a ransom note demanding $500, but the police determined that this was a hoax — though they charged no one.

Dennis Martin, then six, was on an annual Father’s Day camping trip at Smoky Mountain National Park when he went missing in 1969, according to HowStuffWorks. Martin and his brothers had planned to jump out at the adults from different parts of the camp to scare them. They jumped out. Martin didn’t.

Dark Tales described how the family, along with park rangers, hikers, and even U.S. Army Green Berets — 1,400 people in total — tried to find him. Given his red shirt, it should have been easy, but it also rained heavily that night, washing away potential clues. Even park ranger Dwight McCarter, who had tracked down hundreds of missing hikers, had to admit that Martin left no traces. However, all the people searching may have obscured Martin’s tracks.

A nearby family reported that they had heard a scream the evening Martin went missing and saw a “bear-man” with something over its shoulder. However, this lead was not followed up. Mysterious Universe quoted a supposed retired Army SOCOM Commander saying of this search, “Our Special Forces are NEVER called to assist in civilian operations. … The fact that they were armed as well is another huge no-no. … Something is very wrong with this missing kid scenario.”

A man informed authorities in 1985 that he had found a child’s skeleton but did not tell anyone at the time because he had been illegally collecting ginseng and did not want to be prosecuted. When people went to check this lead, they found nothing.

For almost 20 years, Thelma Pauline Melton regularly hiked the Deep Creek Trail in the Smoky Mountains, where she went missing on September 25, 1981. Unsolved Appalachia states that she went there that fateful day with two friends and her husband Bob, who was 20 years older than Melton and not up for hiking. According to The Doe Network, Melton was overweight, had high blood pressure, and needed medication, so she was unlikely to stray far.

The Deep Creek Trail is listed as easy, so no terrain should have proven challenging for the 58-year-old. During the hike, Melton began walking faster, leaving her two friends behind. When they finished the same path and returned to the trailer 30 minutes later, Melton was not there. Within an hour and a half, she was reported missing. That week, more than 150 people and nine dogs searched the trail, but nothing turned up.

In the aftermath, Melton’s pastor implied that she might have been having an affair but provided no evidence. There was also the suggestion that she might have harmed herself, but the evidence for this was scant. (Her mother died that year, and her husband’s bottle of Valium was missing.) Before going for the hike, she had prepared spaghetti sauce for dinner that night, more than suggesting that she intended to return.

Shawn Higgins knew the Siskiyou Mountains in Southwest Oregon well. He skipped school with his girlfriend at 15 to go turkey hunting there. Years later, his girlfriend Stephanie had become his wife, he had raised two sons, and the mountains were “a place for [his] family.”

Shawn and Trevor, his 21-year-old son, had gone out hunting on October 14, 2016. They separated, but the plan was to meet at the truck later to pick up Trevor’s uncle, who was hunting in a different part of the woods. Trevor waited by the road with a freshly killed buck, but his father never arrived. Trevor and his uncle looked for Shawn, to no avail. So that he would not get lost himself, Trevor built a shelter once night fell. Higgins hadn’t brought his backpack with him, expecting that he would not be in the woods long. In the bag was a GPS, which would have allowed his family to find him.

Four days later, Trevor was found a few miles from where he had begun his own search. Stephanie found this bittersweet, KOBI 5 reported. She had hoped until then that Trevor was with his father. When medics airlifted Trevor, he was suffering from severe hypothermia. Hundreds of people took up the search for Shawn, but nothing was found. Not a scrap of cloth. Not bullets.

NBC News quoted Stephanie: “I know he didn’t just get lost. Something happened to him.”

Samantha Sayers left at 8 a.m. on August 1, 2018, for a solo hike in the North Cascades mountains in Washington. According to Strange Outdoors, she had expected to check in on her boyfriend by 6, since he had work and could not join her. By 8 p.m., he was at the trail, trying to track her down. At 1 a.m., her family reported her missing. 

The Vesper Peak Trail is not meant for novices. Hikers have called the trail “hard to follow.” However, Sayers was far from a newbie and had hiked there before.

The search for Sayers was one of the most intensive Snohomish County authorities had undertaken, involving 14 dog teams and helicopters with thermal imaging cameras, GoErie reported. Drones canvassed the area. Volunteer searchers left bags containing supplies, along with notes reading, “Stay Strong! We’re looking for you. Everyone is thinking of you.” Police interviewed witnesses who saw her ascend, but no one admitted to seeing her return. (As she was bald owing to alopecia, she was more noticeable.) She had lunch near the peak with an unknown man at around 3 p.m., but they went their separate ways afterward.

After three weeks, the official search was called off. Search and Rescue Sgt. John Adams said, “If there was a place we thought she could get to, we put people there to look for Sam, often putting our volunteers and personnel at great risk due to the rugged, remote, and dangerous terrain.”

Stefan Bissert, a German exchange student and Fulbright scholar at Oregon State University, went hiking in Olympic National Park on January 20, 1992. The Seattle Times reported that he brought a buddy with him, Gerd Forstmann. They had intended to hike to Deer Lake, which would have been about 4 miles.

However, Strange Outdoors detailed, he made the mistake of leaving Forstmann behind — who was drying off after a swim in a frozen lake — so he could hike 23 miles to the Hoh River trailhead. The Kitsap Sun pointed out that such a hike through the snow in one day would have been close to impossible for him and that few experienced mountain climbers would attempt it — and Bissert, though healthy, was in no condition for this. Kent Heathershaw, Olympic College basic mountaineering instructor, said, “For a single person to walk through snow like that — it’s really impossible.”

When Bissert did not make it, Forstmann reported him missing on January 21. The path he would have had to have taken would have sent him through the Olympic high country and an unforgiving winter storm that lasted for a week, which impeded rescue efforts. Bissert, like others on this list, had not dressed for an ambitious hike or to camp overnight in snow. He had a pack containing only a few pieces of fruit.