First time the town was mentioned in the beginning of 18th century. In 1790 the town received a city privilege, and could arrange its own fairs and shops. At that time the surrounding territories belonged to landlords Sveikauskas family, who in 1787 built the first church in the town. In 19th century the territory passed into the ownership of Gurskis family.
The wooden church of St. Cross Finding was rebuilt in 1851. In the graveyard of the church there is a chapel-column in remembrance of poet and priest Silvestras Gimzauskas (1845 – 1897). He is origin from Utena, and in 1892 started to pastorate in Bagaslaviskis. He got seek and went to Warsaw where he died, and was buried.
Not far from Bagaslaviskis there is a Seiniunu village. Poet Ignas Seinius (Jurkűnas) (1889 – 1959) is origin from this village. He was working as a diplomat in Denmark, Sweden, and Finland. In 1940, when Lithuania was occupied by the Soviets, he illegally crossed the border and went to Sweden through Germany. In 1943 he got Sweden citizenship, and became famous after he published the essay “Raudonasis tvanas” in 1940. This essay is about events that were happening in Lithuania since October 1939 till the summer of 1940. He is one of the most famous 20th century Lithuanian novelists. There is a wooden column in remembrance of the writer.