First a little history. In the old days — we're talking steamships — there were two kinds of tags for luggage. Best known are the labels affixed to trunks. Often these were pure advertising for the shipping line, with no room for personal information. The other kind of tag — a destination tag — was more practical, though still aesthetically pleasing. One side often bore the line's logo, as in this classic Cunard White Star tag. The reverse held information such as the passenger's name, destination, stateroom and whether the bag was "Wanted in Stateroom" or "Not Wanted on Voyage."
Early on, airlines offered labels that mimicked maritime-style advertising stickers, with lovely results. But initially, airlines had no need for destination tags: As the International Air Transport Association explained to me, "a passenger's chauffeur would drive the passenger to the aircraft side, and stewards would load the passenger's bags directly from the car to the aircraft." Nice.
As air travel expanded beyond the perfumed realms of the chauffeured, destination tags became a necessity. Maritime tags were the model, but with the occasional important tweak, as Melissa Keiser, an archivist for the National Air and Space Museum, points out. What is inconsequential to ocean liners and railways, but vital to airlines? Weight. It's critical that airlines know how much bags weigh, and how they're distributed around the plane. According to Keiser, a space for weight was commonplace on airline tags by the 1920s. "Separable" baggage tags, which featured a removable receipt for travelers, had first been developed for railways in 1882. By the 1930s, says Keiser, they too had been widely adopted in aviation.
But as aviation grew still further, airline tags shed their maritime and railway heritage. Compare the two tags here: a Pan Am tag from the 1950s, and a modern tag of the sort an airline will put on your bag today.