St. Louis IX

In 1239 Louis IX of France bought the Crown of Thorns from Baldwin II, the Latin emperor of Constantinople, who had pawned it to Venetian bankers to pay his debts. The king met the relic at Villeneuve-l'Archevêque and walked the last stage into Paris barefoot, carrying it himself. He then built the Sainte-Chapelle to house it, consecrated in 1248 — a reliquary the size of a church, its upper chapel walled almost entirely in glass. The relic cost him more than twice what the building did.

Louis was born at Poissy in 1214 and reigned for forty-three years. He founded the Quinze-Vingts hospital for the blind, sat in judgment under the oak at Vincennes in the account left by his companion Joinville, and led the Seventh Crusade to Egypt, where he was captured at Fariskur in 1250 and ransomed. He took the cross a second time in 1270 and died of dysentery in the camp before Tunis on August 25 of that year. Boniface VIII canonized him in 1297, the only king of France ever canonized.

The Crown of Thorns is kept at Notre-Dame de Paris, and the Sainte-Chapelle stands on the Île de la Cité as the building made for it. His name travelled: the French founders of a Mississippi trading post named it for him in 1764, and St. Louis in Missouri carries the crusading king's name into the American Midwest, its Old Cathedral dedicated to Louis King of France.