West Francia extended further south than modern France, but it did not extend as far east. By the 10th century the rule of its kings was greatly reduced and it did not include Lorraine, Burgundy, Alsace and Provence, nor Normandy which was given to Normans in return for the end of raiding. In Brittany and Catalonia the authority of the West Frankish king was barely felt. West Frankish kings were elected by the secular and ecclesiastic magnates, and for the half-century between 888 and 936 they chose alternately from the Carolingian and Robertian houses. By this time the power of king became weaker and more nominal, as the regional dukes and nobles became more powerful in their semi-independent regions. The Robertians, after becoming counts of Paris and dukes of France, became kings themselves and established the Capetian dynasty.
In August 843, after three years of civil war following the death of Louis the Pious on June 20, 840, the Treaty of Verdun was signed by his three sons and heirs. The youngest, Charles the Bald, received western Francia. The contemporary West Frankish Annales Bertiniani describes Charles arriving at Verdun, "where the distribution of portions" took place. After describing the portions of his brothers, Lothair the Emperor (Middle Francia) and Louis the German (East Francia), he notes that "the rest as far as Spain they ceded to Charles". The Annales Fuldenses of East Francia describe Charles as holding the western part after the kingdom was "divided in three".
Since the death of King Pippin I of Aquitaine in December 838, his son had been recognised by the Aquitainian nobility as King Pippin II of Aquitaine, although the succession had not been recognised by the emperor. Charles the Bald was at war with Pippin II from the start of his reign in 840, and the Treaty of Verdun ignored the claimant and assigned Aquitaine to Charles. Accordingly, in June 845, after several military defeats, Charles signed the Treaty of Benoît-sur-Loire and recognised his nephew's rule. This agreement lasted until March 25, 848, when the Aquitainian barons recognised Charles as their king. Thereafter Charles's armies had the upper hand, and by 849 had secured most of Aquitaine. In May, Charles had himself crowned "King of the Franks and Aquitainians" in Orléans. Archbishop Wenilo of Sens officiated at the coronation, which included the first instance of royal unction in West Francia. The idea of anointing Charles may be owed to Archbishop Hincmar of Reims, who composed no less than four ordines describing appropriate liturgies for a royal consecration. By the time of the Synod of Quierzy (858), Hincmar was claiming that Charles was anointed to the entire West Frankish kingdom. With the Treaty of Mersen in 870 the western part of Lotharingia was added to West Francia. In 875 Charles the Bald was crowned Emperor of Rome.
The last record in the Annales Bertiniani dates to 882, and so the only contemporary narrative source for the next eighteen years in West Francia is the Annales Vedastini. The next set of original annals from the West Frankish kingdom are those of Flodoard, who began his account with the year 919.
After the death of Charles's grandson, Carloman II, on December 12, 884, the West Frankish nobles elected his uncle, Charles the Fat, already king in East Francia and Kingdom of Italy, as their king. He was probably crowned "King in Gaul" (rex in Gallia) on 20 May 885 at Grand. His reign was the only time after the death of Louis the Pious that all of Francia would be re-united under one ruler. In his capacity as king of West Francia, he seems to have granted the royal title and perhaps regalia to the semi-independent ruler of Brittany, Alan I. His handling of the Viking siege of Paris in 885–86 greatly reduced his prestige. In November 887 his nephew, Arnulf of Carinthia revolted and assumed the title as King of the East Franks. Charles retired and soon died on January 13, 888.
In Aquitaine, Duke Ranulf II may have had himself recognised as king, but he only lived another two years. Although Aquitaine did not become a separate kingdom, it was largely outside the control of the West Frankish kings.
Odo, Count of Paris was then elected by nobles as the new king of West Francia, and was crowned the next month. At this point, West Francia was composed of Neustria in the west and in the east by Francia proper, the region between the Meuse and the Seine.