Kuusankoski (as a municipality, not the settlement), was founded in 1921 from the parts of neighboring Iitti and Valkeala. It gained the status of kauppala (literally "a place of commerce") in 1957 and became a town in 1973.
The history of Kuusankoski during the last one and a half centuries has been closely linked to the establishment of the paper factories and their development. The establishment of the factories dates back to the 1870s and 1890s, when the rapids of the river Kymijoki were made to deliver electricity to a waking industry. Since then, and until the modern age of automation, the factories have offered jobs to many generations of Kuusankoski citizens, making the area somewhat more prosperous than the neighboring regions. Today, the influence of the factories on everyday life has somewhat lessened, but their historical importance remains well known
