Nessonvaux is a town and sub-municipality of the Belgian municipality of Trooz on the Vesdre, where the Vaux (also: Ry de Vaux) flows from the Plateau of Herve into the Vesdre. The slopes of the Vesdre valley are steep and wooded. It used to belong to the Prince-Bishopric of Liège, under the tutelage of Fléron. From around 1500 the village developed around a forge, the Cour Monville. In the 19th century, industry came to Nessonvaux. A poor emigrant family from the United States, the Riga family, settled there and brought with them some damask steel gun barrels. These were since produced in large numbers in Nessonvaux for the American Civil War (1861-1865). Almost all water mills in the area, which had previously milled grain, were converted for the manufacture of gun barrels. Factories were built with forging hammers and numerous small forges were also built. Another industry was wool spinning. The Imperia automobile factory was also located in Nessonvaux from 1904 to 1958.