The municipality had a population of 1,293 (2003) and covered an area of 307.93 km2 of which 77.34 km2 is water.

The Swedish name is now considered outdated according to the Institute for the Languages of Finland.

[2] The toponym Sumiainen was first mentioned in 1442 as Sumiais, referring to the nearby lake.

The settlement was established sometime in the 16th century, when it was a part of the Rautalampi parish.

[3] Media related to Sumiainen at Wikimedia Commons