Haapajärvi
Neighbour municipalities are Haapavesi, Kärsämäki, Nivala, Pihtipudas, Pyhäjärvi, Reisjärvi and Sievi.Haapajärvi was first mentioned in 1548 as Hapaierffue (a Swedish transcription of the Finnish name), when it was a part of the parish of Kalajoki.According to the oldest known (1547) tax documents regarding the area, at least half of Haapajärvi's inhabitants were Savonians.Due to this, the area of Haapajärvi (including Pidisjärvi) was known as Kalajoen Savo in the 16th century.Savonian influence is still present in the Central Ostrobothnian dialect spoken in Haapajärvi.