Matamoros

In the U.S. Civil War, by 1862 the Union had blockaded all Confederate ports. Just across the Rio Grande from Brownsville, Texas, Matamoros was the only harbor where the South could ship its cotton to Europe, and smuggle in arms for the rebellion. So it was a haven for Yankee and Rebel spies and diplomats, gunrunners and cotton smugglers, runaway slaves, bandits, Texas Rangers, and rogues of every stripe.

But Matamoros was also full of French Foreign Legionnaires – because that same year, Na...