The Wallonian sillon industriel or dorsale wallonne (French for industrial valley or Wallonian backbone, respectively) was an area of roughly 1000 km² running across Belgium from Dour, in Borinage, in the west, to Verviers in the east. It passes through Mons, La Louvière, Charleroi, Namur, Huy, and Liège, following the valleys of the rivers Haine, Sambre, Meuse and Vesdre. It is not a strict definition of physical geography, but rather refers more to human geography and resources. As heavy industry is no longer the prevailing feature of the Belgian economy, it is now more common to refer to the area as the former sillon industriel.
Around two-thirds of the population of Wallonia lives in the area, over two million people. Its main stretch is the Sambre-and-Meuse valley, sometimes called the Charleroi-Liège valley, which connects Charleroi and Liège. Some see it as a Wallonian metropolis, albeit much more linear and less centralized than most.
The region has seen numerous general strikes, some with social aims, some with political aims. In 1886, due to economic crisis, lowering of salaries and unemployment; in 1893, 1902 and 1913, as a struggle for universal suffrage. More strikes occurred in 1932 and 1936, with a strike in 1950 on the question of the return of Leopold III to the Belgian throne. The region was at the heart of the general strike of winter 1960-1961, which helped Wallonia to gain autonomy. It was also the site of the first dechristianisation in Belgium, and the most ferocious opposition to Leopold III.