It was created after an intermittent civil war by the Treaty of Verdun in 843, given to Lothair I, the eldest son and successor of Louis the Pious. Lothair received Middle Francia and because of his seniority he was also given the Imperial title. His realm contained the imperial cities of Aachen, the residence of Charlemagne, as well as Rome.
It was in its turn divided at the death of Lothair in 855, into three portions which would later become nominally part of the Holy Roman Empire, Lotharingia, the kingdom of Arles and the kingdom of Italy
Middle Francia was situated between the realms of East and West Francia, and comprised the Frankish territory between the rivers Rhine and Scheldt, the Frisian coast of the North Sea, the former Kingdom of Burgundy (except for a western portion, later known as Bourgogne) and Provence, as well as parts of Italy.
Partition of 855
In 855, on his deathbed at Prüm Abbey, Emperor Lothair I in the Treaty of Prüm apportioned Middle Francia amongst his sons. He bequeathed the lands in northern Italy, which extended as far south as Rome and Spoleto, to his eldest son, Louis II the Younger, crowned co-Emperor in 850 and sole Emperor in 855. This became the Kingdom of Italy. Most of the lands north of the Alps, comprising the Low Countries, the western Rhineland, the lands today on the border between France and Germany, and what is now western Switzerland, passed to Lothair II and named Lotharingia, after its ruler. Charles received Upper Burgundy and Lower Burgundy and Provence, which became the Kingdom of Arles, after Charles' capital.
Following the 855 partition, Middle Francia became only a geographic term.
Upon Charles' early and heirless death in 863 his brothers, Louis II and Lothair II, divided his realm. Lothair II received the western Lower Burgundian parts (bishoprics of Lyon, Vienne, Vivarais and Uzès) which were bordering his western Upper Burgundy (remnants of his original Burgundian possessions) which were incorporated into Lotharingia; while Louis II received the Kingdom of Provence.
Then, Lothair II died in 869, and his only son, Hugh, by his mistress Waldrada, was declared illegitimate, so his heir was his brother, Louis II. If Louis II had inherited Lotharingia, Middle Francia would have been reunited. However, as Louis was at that time campaigning against the Emirate of Bari, Lotharingia was partitioned by and between his uncles Charles the Bald and Louis the German by the Treaty of Meerssen (870). Louis the German took Upper Burgundy, territory north of the Jura mountains (Bourgogne Transjurane), while the rest went to Charles the Bald (West Francia).
In 875, the last of Lothair I's children, Louis II, died heirless and naming as his successor in Italy his cousin Carloman, eldest son of Louis the German. However, Pope John VIII, dealing with the constant threat of raiders from the Emirate of Sicily, sided with Charles the Bald. After much confusion and conflict, Charles the Bald took Louis' realm in Italy. Carloman was crowned King of Bavaria in 876 and invaded Italy in 877 to claim the Kingdom of Italy, but on his death in 880 without any legitimate heirs, his kingdom went to his younger brother, Charles the Fat. Charles was crowned Emperor by Pope John VIII in 881 and reunited the entire Carolingian Empire in 884, though the united empire lasted only until Charles' death in 888, when it split again.
- Engreen 1945, p. 325.
- John M. Riddle: A History of the Middle Ages: 300–1500. Rowman & Littlefield Publishers, 2008. ISBN 978-0742554092.
- Timothy Reuter (ed.): The New Cambridge Medieval History, Volume 3: c. 900–c. 1024. Cambridge: Cambridge University Press, 2005. ISBN 9780521364478.
- Engreen, Fred E. (1945). "Pope John the Eighth and the Arabs". Speculum 20 (3): 318–30.