When Hugh Capet was elected king of the Franks by the great feudal lords after the end of the Carolingian dynasty, northern France had been fragmented into numerous fiefs of varying size and importance. The king's revenue came only from his personal demesne, which in 987 was merely the modern-day Ile-de-France, the Orléanais, and some small fiefs on the English Channel. Furthermore, other than these territories, the king did not personally rule over any part of what is now France; he merely received the homage of those who did. Twelve of these lords were known as the peers, because within their territories, their authority was as complete as the king's within his, which included the Droits Régaliens. Some of these peers were actually richer and more powerful than the king himself, a notable example being the counts of Champagne.
Now, if feudalism had created the independence of these fiefs, it also contained the means of their subjugation. Because a fief was personal property, it could be sold, inherited, given, or exchanged. The direct Capetians and their successors used all of these methods to extend their authority over the surrounding territory.
Sometimes, the territories in question became incorporated into the kingdom of France (ex. Champagne), and in some cases, they remained the personal property of the individual who happened to be king (ex. Brittany). Things could get complicated when buying or inheriting a fief made the king a vassal of the Emperor.
In 1205 Philip Augustus confiscated Normandy from its duke, King John of England, for having failed in his feudal obligations.
In 1284 Philip the Fair married Jeanne of Navarre, countess of Champagne. Their son, Louis X, became king of France and count of Champagne. In 1328 Champagne was incoporated into the royal demesne.
In 1349 Humbert II, Dauphin of Viennois sold his fief to Philip VI, who wanted it for his grandson, Charles. The Viennois became the traditional fief of the heir apparent to the French throne, until Louis XI, who kept it even after becoming king. Henceforth, the heir apparent enjoyed the title of Dauphin de Viennois, but not the usufruct of the Dauphiné.