The story
The name of Karstula is likely derived from the Savonian surname Karstunen, encountered around Ristiina since 1541. First records of the surname in Northern Tavastia (modern Central Finland) are from the 18th century. Karstula was initially a part of the Saarijärvi parish, acquiring chapel rights in 1775 under it. Karstula was allowed to become a separate parish and municipality in 1858, but separated later in 1887. Kyyjärvi was a part of Karstula until 1929, though it only acquired a separate parish in 1944.
Suomenselkä municipality
Kannonkoski, Karstula, Kivijärvi and Kyyjärvi had planned to merge into the Suomenselkä municipality from January 1, 2022. Karstula, Kivijärvi and Kyyjärvi accepted the merger proposal, but Kannonkoski did not. After Kannonkoski opted out of the planned merger, Kivijärvi also left out. The merger project of the remaining Karstula and Kyyjärvi failed at the Kyyjärvi municipal council meeting held on May 17, 2021, and the Ministry of Finance did not propose a forced merger either.
From Wikipedia’s article on Karstula, shared under CC BY-SA 4.0.5