It started as just a small crew of special agents. Now, much larger and after a century in the business, the FBI is remembering some of its massive manhunts and landmark cases — the crimes of the century.

One of the most prominent cases was the hunt for Bonnie and Clyde.

Bonnie Parker, just 19, was a part-time waitress and already married to a man in prison when she fell in love with small-time thief Clyde Barrow, 21.

Though Clyde was arrested for burglary soon after they met, Bonnie helped engineer his escape, setting off a crime spree across the Midwest and Southwest that terrified, and enthralled, the country.

• Click here to see photos of some of the criminals of the century.

"They were young and very flamboyant" about their criminal activity, said Dr. John Fox, FBI historian, when asked about the public's enduring interest in the couple. Crime always fascinates people, he said, but the couple’s antics were especially shocking.

By the time they were killed in a hail of police bullets in 1934, the couple was believed responsible for 13 murders and numerous robberies.

The story of their pursuit and the details of their murderous journey are just one of the famous cases profiled by the FBI this year in commemoration of its 100th anniversary on July 26.

The intelligence agency got its start in 1908, when Attorney General Charles Bonaparte created a team of special agents under the Department of Justice. It wouldn’t be until the 1923 appointment of J. Edgar Hoover as director that the Federal Bureau of Investigation — as it came to be called in 1935 — would experience its enormous growth.

Below are some of the cases that have gripped the nation throughout the 100-year history of the "G-men," or government men, who have solved these notorious crimes.

The Lindbergh Baby Kidnapping

On a peaceful New Jersey estate about 60 miles from New York City, the baby Charles A. Lindbergh Jr. slumbered undisturbed in his second floor nursery — or so his parents thought.

When the baby’s nurse went to check on him at around 9 p.m. on the night of March 1, 1932, the only trace of the son of famed aviator Charles Lindbergh was a ransom note demanding $50,000 perched on the nursery window sill.

Over 10 ransom notes followed, including one demanding that a Lindbergh intermediary meet the kidnapper, called "John," and discuss ransom money. The kidnapper then met with Dr. John F. Condon and showed him a sleeping outfit which the Lindberghs identified as belonging to their son.

Working off a description provided by Dr. Condon, and using handwriting samples from the ransom notes, the FBI launched a massive investigation.

Tragically, the child was found dead on May 12, less than three miles from the Lindbergh estate. Autopsy results revealed he had died two months earlier, killed by a blow to the head.

The FBI traced a certificate used to cash in the ransom money to a gas station, where an employee had written down the license plate number of the man who cashed it.

"John" was revealed to be Bruno Richard Hauptmann, a German carpenter living in the Bronx. He was arrested, tried and on April 3, 1936, electrocuted for the murder of Charles Lindbergh Jr.

The Unabomber

Another renowned case began in 1978, with the detonation of a homemade bomb on a Chicago campus. With the blast, Ted Kaczynski vaulted himself into the national consciousness.

But it wouldn’t be until 1995 that the nation would know the name of the notorious Unabomber.

In those 17 years, the Unabomber — named by the FBI for the university and airline bombing targets — created increasingly sophisticated bombs, killing three people and injuring 24, and threatening to blow up airliners.

Though the FBI was able to identify several details about the bomber — they believed he had been raised in Chicago and had lived in Salt Lake City — Kaczynski left no forensic evidence that could be traced to him.

Instead, it would be his own manifesto that led to his arrest. The Unabomber sent the FBI a 35,000 word essay on what he believed were the ills of society and his motives for creating the bombs.

The New York Times and the Washington Post agreed to print the Unabomber’s words in hope that it would lead to clues about the identity of the bomber. Thousands called in with tips, but the FBI began to focus on one tipster in particular — David Kaczynski, who thought the manifesto sounded like his troubled brother Ted.

The FBI was able to conclusively prove Ted Kaczynski was the elusive Unabomber thanks to handwriting samples provided by his brother.

When they arrested the scraggly-haired man at his cabin in Montana they found 40,000 handwritten journal pages that described how to make bombs — and also found a live bomb, ready to be mailed.

In honor of the 100th anniversary of the intelligence agency, the Newseum — a museum in Washington, D.C dedicated to journalism — is featuring "G-Men and Journalists: Top News Stories of the FBI’s First Century."

The exhibit includes the Ted Kaczynski's cabin and the electric chair used to execute Lindbergh baby kidnapper Bruno Hauptmann, in addition to other FBI objects profiling the G-men who solved some of the nation’s most notorious cases.