Somebody had the bright idea to make a tequila Sidecar, using lime juice instead of the lemon and a glass rimmed with salt instead of sugar (tequila popularly being administered with a lick of salt and a slice of lime). The first notice of this practice comes in 1937, from London of all places, where the bartenders at the Café Royal somehow got their hands on a bottle of tequila and did some experimenting. But they called their version the Picador, not the Margarita, and didn't use the salt rim. It's entirely possible that the Margarita was born — in Texas, California, or Mexico — without prior knowledge of the Picador.