When Fletcher Davis (of Athens, Texas) first thought up the hamburger in the 1890s (and served it at the 1904 World's Fair in St. Louis), the condiments that he first went with were onions, pickle slices and a mustard-mayonnaise blend. Still made it tasty, but of course, we're used to a lot more choices now. (Yeah, I know about Louis' Lunch and all the other "first burger" claimants... but as a native Texan I say "fuck y'all". :P)
TRANSCRIPTION COURTESY OF JOSEPH HOUK - [1904, the St. Louis World's Fair] (BG) "Just onions and pickles? No lettuce or tomato? Not even any cheese? What kind of hamburger stand do you run here?" (CW, whispering) "Psst... they just invented the hamburger, dumbass..."