The large rapids of River Kajaaninjoki, Koivukoski and Ämmäkoski, were the biggest obstacles for the oarsmen rowing tar barrels to Oulu. The loads had to be carried by horse and pass the rapids and the fare often comprised 2/3 of the total transport fee from Kuhmo to Oulu. Improvements were demanded for these conditions and in 1822 Vicar Johan Wegelius in Hyrynsalmi pleaded Alexander I, the Emperor of Russia, for his permission to build locks in connection to his locks in Ämmäkoski. The plea was, however, rejected. Johan Wegelius had already built wooden boat channels in 1819 and 1920, but they were not safe and local coachmen had doubts regarding the use of the channels. In 1825, the Emperor gave permission to build canals in the rapids of River Kajaaninjoki. The building project begun in 1836 and the canals were finally completed 11 years later.
In the first years, approximately 6,000 to 10,000 barrels a year were transported through the canals but the numbers increased gradually and at their peak, during the turn of the century, around 24,000 barrels were shipped through the canals. Once the railway was completed in 1904 and as the tar trade decreased, the canals were less busy with the locks being eventually closed on 1 January 1915. The Koivukoski lock was dismantled and the Ämmäkoski lock was filled up with soil. The only tar canal in the world, built in the 1840’s, was eventually closed in 1915 and re-opened in 1984.
Close to the canal is an old lock-keeper’s cottage which was buil in 1880 and originally located right beside the canal. From 1915 to 1917 the cottage was used as a waypoint for troopers and activists. The cottage was shifted a few metres from its original spot to give way to the rebuilding of the canal to transport tar.