Quoted from "History of the Dutch-Speaking Peoples" by Pieter Geyl, 1932

At the outset one great fact claims our attention. It is that in the seventeen Netherlands two races and two civilizations met. By far the larger part of the country was inhabited by a population of Low-Germanic origin and speech. In the southern fringe of provinces, however, the so-called Walloon area - that is in Artois, Walloon Flanders (Lille, Orchies, and Douai), Tournai, Hainaut, Namur, as also in the southernmost district of Brabant (Nivelles) and in the western half of Luxemburg - French was spoken. Trace a line, starting from the North Sea shore in the neighbourhood of Grevelingen, following the rivers Aa and Leie, then, from a point several miles south of Kortryk (Courtrai), continuing in an easterly direction and crossing the Maas several miles south of Maastricht. That line is the linguistic boundary, north of which French was in the position of a foreign language. This, indeed, is still in the main the position today. For many centuries that boundary has hardly moved, so that it still cuts off the northern corner of France and divides Belgium in two almost equal halves. North of it only the towns in the Flemish district annexed by Louis XIV and Brussels have in varying degrees become gallicized.

The origin of this line of demarcation can be exactly indicated. It sprang into being at the time of the great Germanic migrations, in the sixth century, when the people of the Franks, coming from the East, out of the obscure depths of Germania, broke through the Rhine frontier of the crumbling Roman Empire. The country north of the rivers had already for a long time been inhabited by Germanic tribes, some of whom had entertained close relations with the Romans and had undergone their influence very deeply. South of the rivers, too, there were numerous Germanic settlements, although the substratum of the population was probably still Celtic. Incessant raids from the East had in any case so far devastated this region that large stretches were practically empty when the Franks, crossing the rivers Ysel, Rhine, Waal, and Maas, poured down into the valleys of the Scheldt and the Leie. In the course of not very many years they seem to have settled pretty densely most of the land down to the line which still divides the languages. Meantime their most renowned chiefs went on and subjected the Romanized country of Gaul south of that line, which, being more densely populated and more highly organized, succeeded in absorbing their numerous scattered elements.

Two more Germanic tribes helped to compose the population of the Netherlands north of the linguistic boundary - the Frisians and the Saxons; but it was the Franks who, under the Merovingian Kings and their successors, the Carolingians, created the first political organization in which the whole region found a place, and it was their language that became the expression of its unity. The original area of Frankish settlement stretched over Flanders and Brabant right across the rivers into Utrecht and the Veluwe up to the river Ysel. East of that river was Saxon country as far as Friesland and the Ommelands of Groningen, where on the shores of the North Sea the Frisians had their home. At the time of the great Frankish irruption, Holland and Zealand were already settled, but probably very thinly, by Frisians and Saxons. At a very early date, at any rate, that coastal region - with the exception of the small northern part of Holland which long retained the name of West-Friesland - became completely franconized, so that it was differentiated by its language from the northern Frisian as well as from the eastern Saxon areas, while being assimilated to the Frankish territory of Flanders, Brabant, western Gelderland, and Utrecht.

On the basis of linguistic unity there soon arose a common civilization, but political unity proved harder to achieve. In fact, the development of a Netherlands nation and a Netherlands state was from the start seriously impeded by the brilliant career which the leaders of the Frankish race made for themselves in Gaul. Their rise to greatness in that land of superior civilization divorced their interests from those of the bulk of their people, who had stayed behind to settle outlying regions.