Water power was used in the Jämsänjoki valley first to grind grain, and later to grind wood as raw material for paper. The pulp mill was established first in the 1880s and the paper mills followed a good ten years later. Additional raw material for paper manufacture was obtained from two groundwood plants. Soon the paper production was concentrated on more expensive fine grade paper, and the groundwood plants were replaced by power plants generating electricity.

Ever more energy was required for the growing production. Resources of the Jämsänjoki river did not suffice for long, but had to be supplemented by steam, and increasingly from the turn of the 1900s by electricity. The Jämsänkoski factories swallowed up firewood at double the rate of the other United factories. Timber and other raw materials were transported on waterways, and from the 1950s by rail. Trains and ships took the pulp and paper to markets around the world.

The degree of processing was raised by starting manufacture of paper products in the in-house processing section. The residual liquor created by chemical pulp boiling was processed into sulphite spirit, and from the end of the 1970s into Pekilo protein. Development work over many years at the Kaipola factories resulted in a new raw material, thermomechanical pulp, which was to become the primary raw material of both river valley factories.