The Biggest Unsolved Mysteries Of The 1970s

Those that lived through the 1970s look back and fondly remember the decade as a "simpler time" when kids could wander the streets unaccompanied, and hitchhiking seemed like a harmless form of transportation. It was the decade that brought us perms, platform shoes, and a plethora of political upheavals.

Let us not forget this was the era where marginalized groups were gaining more civil rights, the Watergate scandal rocked American politics, the Vietnam War was still dragging along, and the world seemed split between communism and capitalism. Granted, by the end of the decade, the general public seemed less worried about communist takeover than in the previous decade. 

In hindsight, it was every bit as complicated as any other period in history. Serial killers roamed throughout the country, the Satanic panic was gaining steam, and people began to seriously wonder if aliens had been secretly visiting Earth. Somewhere in the middle of all this were some of history's most perplexing mysteries that still remain unsolved. 

In the early days of the airline industry, hijackings were surprisingly commonplace. Between 1968 and 1972, the United States had more than 130 hijackings, as per Vox.

The unknown man people called "D.B. Cooper" perpetrated the only unsolved airline hijacking in America in 1971. According to the FBI, Cooper was a man in his mid-40s who boarded a flight in Portland, Oregon, headed to Seattle, Washington. Cooper silently handed a flight attendant a note that he was carrying a bomb in his attaché case and sent her off to the pilot with his demands: $200,000 in cash and four parachutes.

The passengers on board were released in Seattle, and Cooper was given the ransom and parachutes. While flying to Mexico City, he removed his tie and parachuted out of the aircraft with the ransom money mid-flight and was never seen again. For nearly a decade investigators searched for him. In 1980 a boy discovered a disintegrating package containing nearly $6,000 (in $20 bills) of ransom money.

According to CNN, the FBI found evidence of a new suspect in 2011 when they compared samples to DNA left on Cooper's tie. The problem: This suspect had been dead nearly a decade by the time the FBI received the tip. They did not release the suspect's name or whether they were linked to the crime. Even if he did survive, in all likelihood, Cooper has already died of old age by this point.

In a small quiet suburban town in New Jersey, people began to worry there was a band of Satan worshippers practicing demonic witchcraft after a teenage girl went missing. Jeannette DePalma left home to hitchhike to a friend's house but never returned home, according to Jesse P. Pollack and Mark Moran, authors of "Death on the Devil's Teeth."

Six weeks later, in September of 1972, the 16-year-old was found severely decomposed in the woods on a cliff local residents called "the Devil's Teeth," with several ritualistic items near her body, notes the New York Post. Investigators found DePalma face down with her left arm tucked under her head, several logs arranged around the body like a coffin, and several crosses nearby. 

During the autopsy, the medical examiner noted DePalma had no sign of drugs or substances in her system, but they did find evidence that suggested she could have been strangled (via the New York Post).

Fascinated by the case, editors from the magazine Weird NJ began looking into the murder in 1997. They claimed police resisted giving them any information on the case, explaining that Hurricane Floyd had destroyed all files and evidence in 1999. The editors eventually gained access to the files from the Union County Prosecutor's Office in 2021 and determined that, at least, there was no occult activity. In 2022, an updated version of "Death on the Devil's Teeth" revealed the incarcerated serial killer Richard Cottingham made statements to Pollack that heavily implied he might have been DePalma's murderer, although as of this writing he has not been charged.

Jimmy Hoffa's disappearance in 1975 is one of the most high-profile cold cases in America. Even now, investigators are not truly sure of where his remains lie after he was murdered. He was well-known as president of the International Brotherhood of Teamsters labor union for nearly 15 years (via Britannica). Hoffa was also known for having shady associations.

It was circulated widely that he had connections to organized crime -– specifically the Mafia. The New York Times reports, on July 30, 1975, Hoffa went to meet with New Jersey Mafia boss Anthony Provenzano at the restaurant Machus Red Fox in small-town Michigan. Sometime after arriving, Hoffa vanished.

Many theories of how Hoffa was killed and where his remains are have been debunked, but according to NBC New York, people have claimed he was abducted by federal agents and tossed from an airplane into Lake Michigan, that an associate Frank Sheeran murdered him (this one was featured in the 2019 film "The Irishman"), or that he was buried under a swimming pool in Hampton Township, Michigan.

The most plausible and recent theory being investigated by the FBI is that Hoffa was executed by Provenzano and then had his body loaded into a steel drum before being buried in a landfill in New Jersey. As the New York Times reports, in 2020, a former landfill worker told a friend that his father claimed he buried Hoffa there. The FBI later got the tip and began surveying the site in 2021, although they later announced that "nothing of evidentiary value was discovered."

Between 1976 and 1977, an unknown murderer abducted and killed at least four children in the Oakland County area of Michigan. The known victims were Mark Stebbins, Jill Robinson, Kristine Mihelich, and Timothy King. 

According to "Wolf in Sheep's Clothing: The Search for a Child Killer," by Tommy McIntyre, the children had three key things in common: They were all between 10 and 12 years old, they all lived in affluent neighborhoods in Oakland County, and they were confirmed to be killed by the same individual.

ClickOn Detroit reports the perpetrator had asphyxiated all of the victims (with the exception of Robinson, who suffered a shotgun wound to the head) and would leave the victim's bodies on the streets, staged with their clothes cleaned. Investigators also discovered both boys had been sexually assaulted prior to death and noted all the children had been fed and cared for while captive.

CBS Detroit revealed in 2011 that investigators found new DNA evidence identifying a new suspect. DNA from hairs found on Mihelich matched a man named James Vincent Gunnels, who was 16 at the time. Unfortunately, there was not enough evidence for a trial. While he is not thought to be the Oakland County Child Killer, investigators believe he may have been used to lure victims. Investigators say Gunnels was an associate of key suspect Christopher Busch (as per CBS Detroit).

Millions of people around the world to some degree believe in at least the possibility of intelligent life out there. Back in 1977 one astronomer certainly may have thought he intercepted an alien signal. The "Wow!" signal was found using the now-defunct Big Ear radio telescope that was built for SETI, or the search for extraterrestrial intelligence. One day while checking the printouts from the telescope's computer, Jerry Ehman discovered a code that read "6EQUJ5" (via Astronomy.com).

The code meant Big Ear had picked up a signal — a loud, narrowband originating from the general direction of the constellation Sagittarius. According to Ehman (via Bigear.org), "a few pages into the computer printout I was astonished to see the string (sequence) of numbers and characters ... I immediately highlighted those six characters and wrote the notation 'Wow!' in the left margin of the computer printout opposite them." The signal lasted 72 seconds and was never heard again.

Astronomers searched the region where it first came from but were unsuccessful at finding the source of the signal. Many theories have come about since its discovery in 1977. Antonio Paris, an astronomer from St. Petersburg College in Florida, thinks the signal was possibly from a comet, Live Science reports. 

Live Science states several other factors could explain the Wow! Signal. One of them is a mechanical issue — it is possible Big Ear had a glitch that produced the sound. It could have also just been a result of radio bursts (FRBs) that generate irregular signals.

There was no name on the Circleville letters, just a postmark from Columbus, Ohio. According to Gizmodo, the letters contained handwritten details with accusations and even threats to people's lives. The author claimed to know their every move and planned to expose their dirty secrets if the targets failed to comply with the author's demands. 

As per CBS News, one letter in 1977 accused a school bus driver, Mary Gillispie, and the school superintendent, Gordon Massie, of having an extramarital affair. Mary's husband, Ron Gillispie, was threatened with death if he did nothing to end the affair. Ron grew tired of the harassment and took matters into his own hands. One day he left home armed with a gun but never returned. Police found him later the same day, dead inside his car (which was smashed into a tree) and a single shot fired from his revolver. Authorities ruled his death an alcohol-related car accident (via Gizmodo).

In 1983, Mary was nearly killed by a booby trap. A sign along her bus route was rigged to a box with twine, reports CBS News, and inside the box was a loaded gun. According to History, Mary's ex-brother-in-law, Paul Freshour, was wrongly condemned by police. Even though he had an alibi, he was sentenced to prison. Outside, hundreds of letters continued to circulate to residents.

In 1994 the letters randomly stopped, after Freshour was released, notes CBS. Authorities closed the case never learning who was the hand behind the pen strokes.

Charles C. Morgan was a successful escrow agent and doting father and husband when he was murdered in Tucson, Arizona, in 1977. However, there were hints of trouble when he disappeared for the first time in March, details Unsolved.com. Three days later, he turned back up at his family home drugged and bruised (via "Unsolved Mysteries"), later telling his wife, Ruth Morgan, he had been working undercover for the United States Treasury for about two years on a case and allegedly was involved with at least one mafia member.

Just two months after the initial disappearance, Morgan vanished yet again. This time, according to Tucson.com, Morgan was discovered dead near his vehicle 40 miles from Tucson, clad in his ballistic vest. He had been shot in the back of the head with his own revolver, but investigators found no incriminating fingerprints on the weapon. About two days before the discovery of his body, Unsolved.com reports a mysterious woman called the Morgan residence, saying, "Chuck is all right. Ecclesiastics 12, 1 through 8" before hanging up. The mystery woman would later reveal herself to the sheriff's department as a known associate of Morgan's. She told police Morgan planned to pay off a hitman (hired by the mob) to spare his life, Unsolved.com reports.

Out of all the items collected for evidence, there was a peculiar item pinned to his underwear: a $2 bill. The bill had a rudimentary map of the Arizona-Mexico border drawn on the back, several names in Spanish, and the words "Ecclesiastes 12" and "1 through 8." Despite the strange circumstances, Morgan's death was ruled a suicide by the authorities. 

Interestingly, when journalist Don Devereux looked into the case, he found the FBI claimed to have never known or worked with Charles Morgan.

Could a UFO be the reason 20-year-old Australian Frederick Valentich suddenly vanished in 1978? Valentich had rented a single-engine Cessna 182L to fly to King Island for a dinner date. According to Plane and Pilot Magazine, he was flying over the Bass Strait in Australia when he reported to air traffic controllers that he was being followed by an unidentified flying object.

Valentich continued to report to controllers that the object seemed stationary at some points and then claimed it was hovering over him. At this point, about an hour into the flight, Valentich reported engine roughness. It was his last transmission. The search conducted for him afterward found no body, no airplane, zero results. The Herald Sun reports the investigation by the Department of Transportation offered several possible explanations: a "UFO intervention," spatial disorientation, a hoax planned by Valentich, or a crash where the aircraft could not be recovered. 

It should be noted that Valentich believed in alien sightings. A week before his fateful flight, Valentich told his girlfriend he had been abducted by a UFO and months earlier he gained access to information from the Royal Australian Air Force on UFOs. 

The more logical explanation is that Valentich, being a novice pilot with only 150 hours of flight time, could have simply become disoriented (via Plane and Pilot Magazine). Valentich could have also inadvertently become inverted causing the gravity-fed fuel engine to cut out.

Deputy Sheriff Val Johnson of Minnesota claimed to have had an encounter with a UFO in 1979 — a familiar tale an alien sighting by a single person witnessing an unexplained bright light on a dark country road.

He claims he was driving down a country road at night when he encountered a beam of light that encapsulated his squad car. The Star Tribune reports Johnson remembers waking up about 40 minutes later with "welder" burns to the face and a raised bruise on his forehead. His squad car was wrecked with a shattered windshield, bent up antennas, a small dent in the hood, and a hole through one of the flashers. Curiously, he noted that his watch and squad car clock had both stopped for about 14 minutes. He reported the accident to dispatch saying that an unknown object attacked his car.

The investigation that followed showed no aircraft had been scheduled to fly or were reported near the road during the incident, as per the MinnPost. Experts from the Center for UFO Studies and Honeywell tested Johnson's vehicle and concluded the damage was caused by an electrical force. In the end, the Marshall County Sheriff's Office failed to reach any conclusions and shut down the investigation, according to the Star Tribune.

Today inquiring minds can visit Johnson's damaged patrol car in Warren, Minnesota, along with copies of case file documents and the dispatch recording.

The Vela was a series of 12 unmanned reconnaissance satellites whose primary purpose was monitoring radiation levels in Earth's atmosphere (via Britannica). On September 22, 1979, satellites detected a double flash somewhere in the South Atlantic, according to the National Security Archive. This incident was shrouded in mystery because the truth (at the time) could have had major geopolitical implications. 

Authorities suspected that Israel and South Africa may have been the culprits. If it was proven true, it would mean Israel had violated the peace treaty President Jimmy Carter had brokered between Egypt and Israel. It was widely believed that the U.S. government covered up the incident. Teams of scientists collected data conveniently supporting the idea that the mystery flashes were common –- not a nuclear explosion.

In November of 1979, a panel of experts convened and was unable to determine a particular cause. They implied it was an equipment issue, that it was a "reflection of sunlight from a small meteoroid or a piece of space debris passing near the satellite," as the National Security Archive reports.

The government has since released declassified information favoring evidence of a secret nuclear test, reports Politico. The documents do not conclusively point to a specific country as responsible, but the general consensus from experts is that Vela did detect a low-level nuclear blast.

The Zodiac Killer murders rocked the nation between 1968 and 1969, thanks in part to a series of cryptic letters he sent to media with details about his crimes, according to Wired. Zodiac's letters have been a point of fascination for people over the decades. The letters contained rants, threats, and information about the murders. Some even contained his name concealed by encrypted characters along with portions of a 408-character cipher that could be used to reveal his identity. This is when Zodiac cemented his legacy and garnered a cult following of amateur sleuths determined to discover the words hidden in his letters.

The killer continued to taunt law enforcement and the general public with numerous cryptic letters well into the early 1970s, as per ZodiacKiller.com. That is until May 1978, when the last letter was mailed to Channel 9 in Los Angeles. Zodiac threatened to kill four celebrities, including one member of the Black Panthers, Eldridge Cleaver. Then Zodiac went silent. 

Wired reports in 2020 a team of amateurs decoded "cipher 340" after decades of being shrouded in mystery. The FBI confirmed their solution was correct. The message reads in part: "I hope you are having lots of fun in trying to catch me ... I am not afraid of the gas chamber because it will send me to paradice [sic] all the sooner because I now have enough slaves to work for me ..." 

No one is sure when the murders stopped and never confirmed the identity of the killer, but the FBI continues to investigate Zodiac.