L'Union was founded in the 1790s after the fusion of
Belbèze and
Cornaudric. After leaving Spain,
Napoleon's troops, under the command of Field Marshal and
Marshal of the Empire Soult, battled there against troops under the command of the
Duke of Wellington. The name ''Saint-Jean-de-l'Union'' is still spoken of, recalling the time when the communes of
Saint-Jean et L'Union were unified. ==Population==