The Zodiac killer terrorized the San Francisco area in the 1960s and 1970s.

Th­ey were gruesome crimes that shocked us with their brutality. But as time passed, we heard less and less about them until we forgot about the crime, not even realizing that the perpetrator remained among us. Yet the files remain open, and the families of the victims live on in a state of semi-paralysis.

Here are some of the world's most famous cold cases.

1. Elizabeth Short

Elizabeth Short, also known as the Black Dahlia, was murdered in 1947. Like thousands of others, Elizabeth wanted to be a star. Unlike the bevy of blondes who trekked to Hollywood, this 22-year-old beauty from Massachusetts was dark and mysterious. She was last seen alive outside the Biltmore Hotel in Los Angeles on the evening of January 9, 1947.

Short's body was found on a vacant lot in Los Angeles. It had been cut in half at the waist and both parts had been drained of blood and then cleaned. Her body parts appeared to be surgically dissected, and her remains were suggestively posed. Despite receiving a number of false confessions and taunting letters that admonished police to "catch me if you can," the crime remains unsolved.

2. The Zodiac Killer

The Zodiac Killer was responsible for several murders in the San Francisco area in the 1960s and 1970s. His victims were shot, stabbed, and bludgeoned to death. After the first few kills, he began sending letters to the local press in which he taunted police and made public threats, such as planning to blow up a school bus.

In a letter sent to the San Francisco Chronicle two days after the murder of cabbie Paul Stine in October 1969, the killer, who called himself "The Zodiac," included in the package pieces of Stine's blood-soaked shirt. In the letters, which continued until 1978, he claimed a cumulative tally of 37 murders.

Still curious about unsolved crimes? Read about more cold cases on the next page.