The core Frankish territories inside the Roman empire were close to the Rhine and Maas rivers in the north. After a period where small kingdoms inter-acted with the remaining Gallo-Roman institutions to their south, a single kingdom uniting them was founded by Clovis I who was crowned King of the Franks in 496. Under the nearly continuous campaigns of Pepin of Herstal, Charles Martel, Pepin the Short, Charlemagne, and Louis the Pious—father, son, grandson, great-grandson and great-great-grandson—the greatest expansion of the Frankish empire was secured by the early 9th century.
The tradition of dividing patrimonies among brothers meant that the Frankish realm was ruled, nominally, as one polity subdivided into several regna (kingdoms or subkingdoms). The geography and number of subkingdoms varied over time, but the particular term Francia came generally to refer to just one regnum, that of Austrasia, centred on the Rhine and Meuse in northern Europe. Even so, sometimes the term was used as well to encompass Neustria north of the Loire and west of the Seine.
Francia is regarded as the common predecessor of the modern states of France and Germany. After the Treaty of Verdun in 843, West Francia became the predecessor of France, and East Francia became that of Germany. Most Frankish Kings were buried in the Basilica of St Denis near Paris. Francia was among the last surviving Germanic kingdoms from the Migration Period era until its partitioning in 843.
The singular use of the name Francia eventually shifted towards Paris, and settled on the region of the Seine basin surrounding Paris, which still today bears the name Île-de-France and gave its name to the entire Kingdom of France. The most prominent other places named after the Franks are the region of Franconia, the city of Frankfurt, and Frankenstein Castle.
The Franks emerged in the 3rd century as a term covering Germanic tribes living on the northern Rhine frontier of the Roman empire, including the Bructeri, Ampsivarii, Chamavi and Chattuarii. While all of them had a tradition of participating in the Roman military, the Salians, were allowed to settle within the Roman Empire. In 357, having already been living in the civitis of Batavia for some time, Emperor Julian, who forced back the Chamavi back out of the empire at the same time, allowed the Salians to settle further away from the border, in Toxandria.