To understand what "pulled" and "pushed" many Belgians to emigrate to North America and elsewhere in the 19th and early 20th centuries, it is best to begin by looking at what happened during the Ancien Régime('old system') during which the Austrian Habsburg monarchs ruled the 'Southern Netherlands' until 1795 and then in the 20 years that the French occupied what later became 'Belgium'.
http://www.rootsweb.com/~belghist/Flanders/index.htm