Short answers, pulled from the story.
The Sillon industriel is a former industrial region running roughly a thousand square kilometers across Wallonia, Belgium, from Dour in the west to Verviers in the east. It follows the valleys of the Haine, Sambre, Meuse, and Vesdre rivers and was the economic core of Belgium during the Industrial Revolution. It is also known as the Dorsale wallonne, meaning the Walloon industrial backbone.
The Sillon industriel was the first fully industrialized region in continental Europe, with its initial industrialization wave occurring from 1800 to 1820. It predated comparable industrial development elsewhere on the continent and made Belgium a leading industrial nation through coal, steel, and heavy manufacturing.
After World War II, the importance of Belgian steel, coal, and heavy industry declined. The region shifted toward non-metallic raw materials such as glass and soda, but that transition lasted only until the 1970s, after which unemployment rose and the region became economically dependent on the formerly poorer Flemish Region.
Major strikes in the Sillon industriel occurred in 1886 due to economic crisis, wage cuts, and unemployment; in 1893, 1902, and 1913 as part of the struggle for universal suffrage; in 1932 and 1936; in 1950 over the return of Leopold III to the throne; and in the winter of 1960-1961, which helped Wallonia gain autonomy.
Four former industrial sites in the Sillon industriel were recognized as a UNESCO World Heritage Site in 2012 under the designation Major Mining Sites of Wallonia.
Over two million people live in the Sillon industriel, which is around two-thirds of the total population of Wallonia. Some observers describe the corridor connecting Charleroi and Liège as a linear Walloon metropolis.