Ultimately, Chambliss's conviction and life sentence in 1977 led to the cooperation of previously reluctant witnesses, and after the case re-opened in the mid-1990s, Blanton and Cherry were convicted and sentenced to life in prison in 2000. Cash had died in 1994.
Wall Street Bombing
One of the first acts of terrorism on U.S. soil still remains a mystery.
The flood of Wall Street lunch-goers didn't notice a nondescript man on a horse-drawn cart outside the U.S. Assay Office on Sept. 16, 1920. After the man quickly disappeared into the crowd, the cart exploded, killing more than 30 people and injuring near 300 as metal fragments rained from the sky.
Speculations of conspiracy and terrorism abounded, but crews cleaned the damage overnight (not realizing they were destroying crucial evidence), leaving almost no clues behind.
The best tip came prior to the explosion. A letter carrier found four crudely spelled and printed flyers in the area from a group demanding the release of political prisoners. The group, called the "American Anarchist Fighters," resembled the Italian Anarchists that used similar flyers in two prior bombing campaigns.
The FBI originally suspected followers of Italian Anarchist Luigi Galleani, but the case couldn't be proved and promising trails became dead ends.
The case remains unsolved.
Hollow Nickel, Hidden Agent
A Brooklyn newspaper boy dropped a nickel in 1953 and the coin split in half, revealing a miniature photograph with a series of numbers too small to see. As he picked it up, he was unaware that he held the nation's security in his hands.
Deemed evidence of counterintelligence, the nickel made its way to the FBI. The bureau began questioning people who handled the nickel and novelty store owners who might sell similar products, but they got no leads. FBI Lab scientists in Washington, however, realized the coin's type-print came from a foreign typewriter, and that the photograph was a coded message, but they couldn't crack it.
Four years later, when Russian spy Reino Hayhanen defected to the U.S., he led agents to a "dead drop hiding place" where the FBI found a hollowed-out bolt with a typewritten message inside.
He shared similar hollowed-out items, including a coin, and the connection was made. Hayhanen aided in cracking the code, which put them on the trail of Soviet spy Colonel Rudolf Abel, who Hayhanen believed to be the nickel's owner.
Abel was convicted and sentenced to jail in 1957, but he evaded his prison time as he was exchanged for an American pilot, Francis Gary Powers, who was shot down over the USSR.
The so-called "Freedom Summer" marked a massive three-month initiative to register southern African-Americans to vote as a counterattack to the Ku Klux Klan's campaign of fear and intimidation.
In June 1964, the Klan in Mississippi responded, targeting New Yorker Michael Schwerner, a key figure in organizing local boycotts of biased businesses and voter registration.
On June 16, acting on a faulty tip, the Klan searched a local church meeting for him. When the discovered he wasn't there they burned the church and beat the churchgoers. Schwerner arrived on June 20 to investigate the fire.
He and two fellow activists were arrested by Deputy Sheriff Cecil Price shortly after leaving the church, allegedly for speeding. KKK members followed Schwerner's car after their release, and the three were never heard from again.
On June 23, the FBI discovered the remains of Schwerner's blue station wagon and commenced a search for the bodies.
More than 15 suspects, including Price, were indicted and arrested.
Years of court battles led to only seven guilty convictions of the 18 defendants, but none for murder charges.
In 2005, the 41st anniversary of the murders, Edgar Ray Killen, one of the conspirators, was convicted of manslaughter.