In 748, the brothers Pepin the Short and Carloman gave their younger brother Grifo twelve counties in Neustria centred on that of Le Mans. This polity was termed the ducatus Cenomannicus, or Duchy of Maine, and this was an alternative name for the regnum of Neustria well into the ninth century.
The term "Neustria" took on the meaning of "land between the Seine and Loire" when it was given as a regnum (kingdom) by Charlemagne to his eldest son, Charles the Younger, in 790. At this time, the chief city of the kingdom appears to be Le Mans where the royal court of Charles was established. Under the Carolingian dynasty, the chief duty of the Neustrian king was to defend the sovereignty of the Franks over the Bretons.
In 817, Louis the Pious granted Neustria to his eldest son Lothair I, but following his rebellion in 831, he gave it to Pepin I of Aquitaine, and following the latter's death in 838, to Charles the Bald. Neustria, along with Aquitaine, formed the major part of Charles West Frankish kingdom carved out of the Empire by the Treaty of Verdun (843). Charles continued the tradition of appointing an elder son to reign in Neustria with his own court at Le Mans when he made Louis the Stammerer king in 856. Louis married the daughter of the King of Brittany, Erispoe, and received the regnum from the Breton monarch with the consent of the Frankish magnates. This unique relationship for Neustria stressed how it had shrunk in size to definitely exclude the Île de France and Paris by this time, as it was distanced from the central authority of Charles the Bald and closer to that of Erispoe. Louis was the last Frankish monarch to be appointed to Neustria by his father and the practice of creating subkingdoms for sons waned among the later Carolings.
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