The Loire Valley and its châteaux were the backdrop to some of the most dramatic events in French history. By Roman times the Loire was one of Gaul’s most important transport arteries. The earliest châteaux were medieval fortresses established in the 9th century to fend off marauding Vikings. By the 11th century massive walls, fortified keeps and moats were must-haves for the region's querulous potentates.
During the Hundred Years War (1337–1453) the Loire marked one of the boundaries between French and English forces, and the area was ravaged by fierce fighting. After Charles VII regained his crown with the help of Joan of Arc, the Loire emerged as the centre of French court life. Charles took up residence in Loches with his mistress, Agnès Sorel, and the French nobility, and from then the aristocracy took to building extravagant châteaux as expressions of their wealth and influence.
François I (r 1515–47) made his mark by introducing ornate Renaissance palaces to the Loire. François’ successor, Henri II (r 1547–59), his wife, Catherine de Médicis, and his mistress, Diane de Poitiers, pursued their bitter personal rivalries from castle to castle, while Henri’s son Henri III (r 1573–89) used Blois’ castle to assassinate two of his greatest rivals before being assassinated himself less than a year later.