Alexandria's police force didn't get cars until 1920.

It wasn't any easier for Alexandria police to catch really bad guys a century ago. Back then, officers relied on a person's facial measurements to make an identification.

Later, when police began using fingerprints, the only tool experts had was their eyes: They looked at a suspect's fingerprints and compared them with fingerprint records kept on cards. The cards were stored in many locations, however, so they had to be collected before the identification process could begin. Matching two sets of prints often took months.

Today, thanks to computers, a match can be made in less than two hours, according to the Federal Bureau of Investigation (FBI). The FBI has kept the nation's fingerprint records since 1924. Currently, the prints of more than 47 million people are stored in its electronic Criminal Master File.

Finding wanted suspects also was more difficult 100 years ago. Posting a notice on the Internet or sending an e-mail wasn't possible, of course. Instead, police departments mailed each other letters (the kind that need postage stamps) or sent telegrams.

For example, if officers in Alexandria were looking for a suspect in a bank robbery, they might write to police departments across Virginia. The letters would include a description of the suspect and a question: Is there anyone fitting this description in your jail?

The system worked, although it could take weeks to get an answer.

—Leef Smith / LATWP