Once an independent county vaguely vassalised by Francia the line of counts ended with the death of Baldwin VII in 1119 whereupon it was inherited by his cousin Charles I of Anglia. This was strenuously resisted by the nominal French overlords but attempts by Paris to dictate who governed the county would ultimately fail. The county would henceforth form an integral, and indeed extremely wealthy part of the Anglian state from that point on.
As the Anglian territories on the continent grew (into Artesië, Hainault and Brabant) so did the wealth generated in the growing merchant cities. The cities took up the wool exports of Anglia then exported fine finished cloth, as well as provided a market for French and Rheinish wine. Alongside the dyking and reclamation of much of the Flemish coast this would turn the county into one of the most urbanized parts of Europe. Help to Emperor Olaf turned the county into a Duchy and an Electorate, giving the Anglian kings a voice in who could govern the Empire and increasing their interference in the affairs of Germany.
This dense population would prove easy prey to the Black Death and, as the foreign ambitions of the Anglian kings grew, so did their reliance on Flemish taxes. By the eve of War of Anglian Succession, though still wealthy, the electorate was losing ground to the home-grown cloth in Anglia, ironically developed by Flemish émigrés. The war would ravage much of Flanders and its attached lands but would remove it from Anglia's sphere. Instead it became a part of the Luxembourg realm, a vast collection of territory which included Brandenburg, Bohemia, Hungary and now a considerable slice of Francia and Holland too.
Flanders would become majority Lutheran during the Reformation and as the eastern European Luxembourg were lost to war and revolt it increasingly became the centre of the Luxembourg realm. The religious situation would trouble its rulers greatly, with frequent repressions, revolts and persecutions, until Henry VIII converted to Lutheranism in 1568. It would happily avoid much of the destruction of the Fifty Years War (which mostly saw action to the north or east of the region) but the war's effects on the whole of Europe were still keenly felt and as trade plummeted and plague swept the region many Flemings would emigrate to fresh areas, either peaceful Anglia or areas of Germany depopulated during the war.
Antwerp officially became the capital of the UKN in 1906 in the Flanders Reform Law which also saw the government of the various counties reorganized as a single kingdom. Flanders would be the first part of the UKN which embraced the Industrial Revolution and the region was soon marked with canals and railways to fuel continued growth. Trade continues to underpin the economy and Antwerp is the second largest port in Europe with much of Europe's oil imports flowing through its docks.