From alien contact to war
Another FBI case that is famous for taking a long time to solve is that of the Unabomber. The Bureau began looking into a series of mysterious bombings in the 1980s.
In the end, it was the brother of perpetrator Ted Kaczynski who alerted the FBI to his potential involvement in the case. Eventually, he was arrested and convicted before dying in prison.
The FBI identified and located the bomber, Timothy McVeigh, in just two days. It then took some time for them to secure a conviction, but eventually, McVeigh was convicted and executed in 2000.
Sources: (History)
The bombing, which took place outside the Alfred P. Murrah Federal Building in Oklahoma City, killed 168 people and injured hundreds more.
They found similarities between bombings that took place between 1978 and 1995, but for decades they were unable to identify the perpetrator.
The Oklahoma City bombings, which took place on the morning of April 19, 1995, are considered the single worst case of domestic terrorism in the United States.
When they finally caught up with her, they found she had joined the ranks of her abductors and helped them to commit various other crimes.
Hearst, who by then went by the name Tania, was charged with bank robbery and other offenses. She was sentenced to seven years in prison.
In 1974, the FBI took charge of the investigation of the kidnapping of heiress Patty Hearst.
D. B. Cooper has never been located, despite the Bureau's investigations into around 800 suspects. In 2025, the case remains open.
It was not until 1994, when Evers's widow convinced the FBI to re-open the case, that De La Beckwith was finally convicted. He died in prison in 2001.
The FBI almost immediately connected the weapon with the culprit, Byron De La Beckwith, but he was not convicted at that point because two all-white juries rejected the testimony of the FBI and other witnesses.
It was an unprecedented hijacking that involved two planes, four parachutes, and a ransom of US$200,000 in used notes.
Perhaps the most famous unsolved FBI case is that of the disappeared plane hijacker, D. B. Cooper. The initial crime took place in November 1971.
In June 1963, civil rights activist Medgar Evers was shot dead on the doorstep of his home in Jackson, Mississippi.
They conducted around 25,000 interviews and whittled down a list of leads in the tens of thousands, ultimately identifying the sole gunman as Lee Harvey Oswald.
Both were convicted of the crime and executed in 1953. There was huge controversy, however, when it was later revealed that the FBI had only pursued the case against Ethel in order to make Julius confess.
The FBI played a key role in investigating the assassination of former President of the United States, John F. Kennedy.
The FBI arrested and investigated various individuals they believed were involved in the spy ring, including engineer Julius Rosenberg and his wife Ethel.
By May 1934, Bonnie Parker and Clyde Barrow were wanted for multiple robberies and murders across large areas of the United States.
During the late 1940s, US military intelligence agents discovered a spy network that was burrowed deep inside the high-security atomic development program at Los Alamos, New Mexico.
After the child's body was discovered two months later, the Bureau launched a huge investigation. One of their tactics was to make public the serial numbers of the gold certificates paid as the ransom.
Quite quickly, however, members of the tribe started dying. There were various unexplained explosions and shootings, about which local law enforcement did nothing.
In March 1932, the young son of famous aviator, Charles Lindbergh was kidnapped. The kidnapper left a ransom note demanding US$50,000, which Lindbergh paid, but the baby wasn't returned.
In the early 1920s, members of the Osage Tribe in north-central Oklahoma became some of the richest people in the world when oil was discovered under their land.
More than a year later, Bruno Hauptmann used one of those notes to pay at a service station. He was arrested and ultimately convicted of the boy's murder in 1935.
When the Bureau of Investigation—as it was known then—stepped in, it used undercover informants to reveal a vast conspiracy, in which white residents of Osage were marrying and then killing rich tribal people. One of the ringleaders in the plot was prominent cattle baron, William Hale.
The Bureau worked with local law enforcement in various different states to track the duo's movements and ultimately coordinate the ambush, which took place in a remote corner of Louisiana.
The crimes of the infamous duo, Bonnie and Clyde, were ultimately brought to a stop by local police officers. However, it wasn't without a huge effort from the Bureau.
When the former President suffered a fatal bullet wound in Dealey Plaza, Dallas, the FBI was almost immediately on the scene, interviewing witnesses and preserving evidence.
The Federal Bureau of Investigation (FBI) was formed in 1908, and over the course of the 20th century it played a key role in investigating the most serious crimes committed in the United States.
With a reputation for working on some of the most complex and perplexing cases ever to cross the desks of law enforcement, in the 21st century the FBI continues to go about its important work.
Check out this gallery to learn about some of the biggest FBI cases of the 20th century.
The biggest FBI cases of the 20th century
Keeping the Bureau busy
LIFESTYLE History
The Federal Bureau of Investigation (FBI) was formed in 1908, and over the course of the 20th century it played a key role in investigating the most serious crimes committed in the United States.
With a reputation for working on some of the most complex and perplexing cases ever to cross the desks of law enforcement, in the 21st century the FBI continues to go about its important work.
Check out this gallery to learn about some of the biggest FBI cases of the 20th century.