Why were the borders of the Brussels-Capital Region limited to 19 communes?

The limitation of the Brussels-Capital Region to 19 communes was a political resolution to the intense linguistic and territorial tensions between Belgium’s Flemish and Walloon communities during the 20th century.

As the metropolitan area of Brussels expanded throughout the 19th and 20th centuries, it became a focal point of conflict. The Flemish population, concerned about the "Frenchification" of the capital and the potential for the metropolis to annex surrounding Flemish-speaking areas, strongly opposed further territorial expansion. Conversely, French-speaking residents resisted efforts to restrict the city's growth, which they viewed as an imposition of a legal "straitjacket" on the capital.1

To settle these disputes, the Belgian parliament passed a law in 1963 that officially restricted the capital to its 19 bilingual municipalities. This measure was designed to halt the spread of Francophone influence into neighboring Flemish regions while simultaneously providing language facilities to French-speaking minorities in several suburban boroughs. This administrative boundary was later solidified when the Brussels-Capital Region was established as one of Belgium's three autonomous regions during the federalization process of the 1980s and 1990s.12