 The borough is part of the Harrisburg–Carlisle Metropolitan Statistical Area.Millerstown is located on a tract of land originally sold to James Gallagher on September 23, 1766, however, there is evidence that a small town named "Smithfield" was founded by him before then.This plot of ground was later sold to David Miller on September 1, 1780, who filed for a patent in 1790 for the "laying out of the town," thus making Miller's Town the first town to be plotted for sale in the territory at that time comprising Perry County.