The sense of "Flemish" identity increased significantly after the Belgian Revolution. Prior to this, the term "Flemings" in the Dutch language was in first place used for the inhabitants of the former County of Flanders. Flemish however had been used since the 14th century to refer to the language and dialects of both the peoples of Flanders and the Duchy of Brabant. The modern Belgian province of Limburg was not part of the treaty, and only came to be considered "Flemish" in the 19th century.
In 1830 the southern provinces of the United Netherlands proclaimed their independence. French-dialect speaking population, as well as the administration and elites, feared the loss of their status and autonomy under Dutch rule while the rapid industrialization in the south highlighted economic differences between the two. Under French rule (1794–1815), French was enforced as the only official language in public life, resulting in a Frenchification of the elites and, to a lesser extent, the middle classes. The Dutch King allowed the use of both Dutch and French dialects as administrative languages in the Flemish provinces. He also enacted laws to reestablish Dutch in schools. The language policy was not the only cause of the secession; the Roman Catholic majority viewed the sovereign, the Protestant William I, with suspicion and were heavily stirred by the Roman Catholic Church which suspected William of wanting to enforce Protestantism. Lastly, Belgian liberals were dissatisfied with William for his allegedly despotic behaviour.
Following the revolt, the language reforms of 1823 were the first Dutch laws to be abolished and the subsequent years would see a number of laws restricting the use of the Dutch language. This policy led to the gradual emergence of the Flemish Movement, that was built on earlier anti-French feelings of injustice, as expressed in writings (for example by the late 18th-century writer, Jan Verlooy) which criticized the Southern Francophile elites. The efforts of this movement during the following 150 years, have to no small extent facilitated the creation of the de jure social, political and linguistic equality of Dutch from the end of the 19th century.
After the Hundred Years War many Flemings migrated to the Azores. By 1490 there were 2,000 Flemings living in the Azores. Willem van der Haegen was the original sea captain who brought settlers from Flanders to the Azores. Today many Azoreans trace their genealogy from present day Flanders. Many of their customs and traditions are distinctively Flemish in nature such as Windmills used for grain, São Jorge cheese and several religious events such as the imperios and the feast of the Cult of the Holy Spirit.
Within Belgium, Flemings form a clearly distinguishable group set apart by their language and customs. However, when compared to the Netherlands most of these cultural and linguistic differences quickly fade, as the Flemish share the same language, similar or identical customs and (though chiefly with the southern part of today's Netherlands) traditional religion with the Dutch. However, the popular perception of being a single polity varies greatly, depending on subject matter, locality and personal background. Generally, Flemings will seldom identify themselves as being Dutch and vice versa, especially on a national level.