The company has a long tradition of forest industries in Finland. There the company's first paper mills and sawmills were put into operation in the beginning of the 1870s. Pulp manufacturing began in the 1880s and paper converting in the 1920s. The company started manufacturing plywood in the 1930s. Several Finnish forest industry companies have merged with the forerunner companies of UPM, such as: Walkiakoski, Jämsänkoski, Kaukas, Halla, Kajaani, Toppila, Kymmene, Kuusankoski, Kymi, Voikkaa, Lohjan Paperi Oy, Wilh. Schauman, W. Rosenlew, Raf. Haarla and Myllykoski.