 The merged towns were known as Mifflinburg before 1827 however, because when Union County was formed from Northumberland County on March 22, 1813, that PA legislative act also established Mifflinburg as the seat of government of the newly formed county, with the first courthouse located at 406 Green Street and other government offices located in various other buildings throughout the town.It remained the county seat until 1815 when it was moved to New Berlin, and then to Lewisburg in 1855 where it remains today.In 1845, George Swentzel set up Mifflinburg's first buggy business.