On the death of Pepin the kingdom was divided between Charlemagne and his brother Carloman (Carloman ruled Austrasia). Carloman died on December 5, 771, leaving Charlemagne with a reunified Frankish kingdom. Charlemagne was engaged in almost constant battle throughout his reign. He conquered Saxony in the 8th century, a goal that had been the unattainable dream of Augustus. It took Charlemagne over 18 times at battle to win this victory. He forced Catholicism on them, and led massive slaughters of those who refused. He dreamed of the reconquest of Spain, but never fully succeeded in this goal. In 800, at Mass on Christmas day in Rome, Pope Leo III crowned Charlemagne emperor, a title that had been out of use in the West since the abdication of Romulus Augustulus in 476. While this title helped to make Europe independent of Constantinople, Charlemagne did not use the title until much later, as he feared it would create dependence on the Pope.
Pursuing his father's reforms, Charlemagne did away with the monetary system based on the gold sou. Both he and King Offa of Mercia took up the system set in place by Pippin. He set up a new standard, the livre (i.e. pound)— both monetary and unit of weight— which was worth 20 sous (as per the solidus, and later the shilling) or 240 deniers (as per the denari, and eventually the penny). During this period, the livre and the sou were counting units, only the denier was a coin of the realm.
Charlemagne applied the system to much of the European Continent, and Offa's standard was voluntarily adopted by much of England.
Charlemagne organized his empire into 350 counties, each led by an appointed count. Counts served as judges, administrators, and enforced capitularies. To enforce loyalty, he set up the system of Missi Dominici, meaning 'Envoys of the Lord.' In this system, one representative of the church and one representative of the emperor would head to the different counties and every year report back to Charlemagne on their status.
After Charlemagne's death, continental coinage degraded and most of Europe resorted to using the continued high quality English coin until about 1100.
It is difficult to understand Charlemagne's attitude toward his daughters. None of them contracted a sacramental marriage. This may have been an attempt to control the number of potential alliances. After his death the surviving daughters entered or were forced to enter monasteries. At least one of them, Bertha, had a recognized relationship, if not a marriage, with Angilbert, a member of Charlemagne's court circle.
It is frequently claimed by genealogists that all people with European ancestry alive today are probably descended from Charlemagne. However, only a small percentage can actually prove descent from him. Charlemagne's marriage and relationship politics and ethics did, however, result in a fairly large number of descendants, all of whom had far better life expectancies than is usually the case for children in that time period. They were married into houses of nobility and as a result of intermarriages many people of noble descent can indeed trace their ancestry back to Charlemagne.
1Up until the mid-20th century, Charlemagne's birthday was believed to be 2 April742, but several factors led to reconsideration of this traditional date. First, the year 742 was calculated from his age given at death, rather than attested with primary sources. The second problem is that 742 preceeds the marriage of his parents (by 744), yet there is no indication that Charlemagne was a bastard, and he inherited from his parents which ought not to have been possible under those circumstances. Another date is that given in the Annales Petarienses2 April747. In that year, 2 April is Easter. Since the birth of an Emperor on Easter is a coincidence likely to provoke comment, there is suspicion evoked by the fact that there is no such comment documented in 747, leading some to suspect the Easter birthday was a pious fiction concocted as a way of honoring the Emperor. Other commentators weighing the primary records have suggested that the birth was one year later, 748. So at present, it is impossible to be certain of the date of the birth of Charlemagne. The best quesses include 2 April747, after 15 April747, or 2 April748.