The FBI had a massive room dedicated to storing fingerprint files
In today’s hyper-connected world, almost every database can be accessed with a button. However, in the past, these databases contained physical files that had to be stored in a brick-and-mortar building. The giant room you see in this picture, taken in 1944, was where the FBI kept all their fingerprint samples.
Experts had to take out the paper files to analyze and compare the prints. There were no special computer programs or Internet connections to aid them. Of course, that meant it took longer to find cross-matches, suggesting that human error was much more common.