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Wikipedia
Louis IX (25 April 1214 – 25 August 1270), commonly Saint Louis, was King of France from 1226 to his death. He was also Count of Artois (as Louis II) from 1226 to 1237. Born at Poissy, near Paris, he was a member of the House of Capet and the son of King Louis VIII and Blanche of Castile. Louis was twelve years old when his father died on November 8, 1226. He was crowned king within the month at the Reims cathedral. Because of Louis's youth, his mother ruled France as regent during his minority. He is the only canonized King of France and consequently there are many places named after him, most notably St. Louis, Missouri in the United States.
Saint Louis ruled during the so-called "golden century of Saint Louis", when the kingdom of France was at its height in Europe, both politically and economically. The king of France was regarded as a primus inter pares among the kings and rulers of the continent. He commanded the largest army, and ruled the largest and most wealthy kingdom of Europe, a kingdom which was the European center of arts and intellectual thought (La Sorbonne) at the time. The prestige and respect felt in Europe for King Louis IX was due more to the attraction that his benevolent personality created rather than to military domination. For his contemporaries, he was the quintessential example of the Christian prince, and embodied the whole of Christendom in his person. His reputation of saintliness and fairness was already well established while he was alive, and on many occasions he was chosen as an arbiter in the quarrels opposing the rulers of Europe. Louis IX is often considered the model of the ideal Christian monarch.
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City of St. Louis Heritage website
Pierre Laclede Liguest, recipient of a land grant from the King of France, and his 13-year-old scout, Auguste Chouteau, selected the site of St. Louis in 1764 as a fur trading post. Laclede and Chouteau chose the location because it was not subject to flooding and was near the confluence of the Mississippi and Missouri Rivers. Construction of a village, named for Louis IX of France, began the following year. Most of the early settlers were French; many were associated with the fur trade. St. Louis transferred to the Spanish in 1770, returned to France under a secret treaty with Napoleon and, following the Louisiana Purchase of 1803, became part of the United States. According to legend, on the day of transfer of the territory to the United States in 1803, St. Louis flew under three flags in one day--French, Spanish, and American.
The town gained fame in 1803 as the jumping-off point for the Louisiana Purchase Expedition of Meriwether Lewis and William Clark. After 1804, more New Englanders and other East Coast emigrants settled in St. Louis, but the population remained predominantly French until well into the 19th-Century. St. Louis incorporated as a city in 1823. During the 19th-Century, St. Louis grew into an important center of commerce and trade, attracting thousands of immigrants eager to find a new life on the edge of the frontier.
~ Heritage & History