Blain is a borough in Perry County, Pennsylvania, United States. The population was 227 at the 2020 census. It is share of the Harrisburg metropolitan area. Blain is located in a valley region known as Sherman’s Valley.

Early agreement began on the order of the mill built by James Blaine in 1778, from whom the borough took its name. The final “e” was dropped at some point, although there are records of county newspapers using the “Blaine” spelling until at least 1868. Early in the 1800s, Blaine’s mill came into the possession of William Douglas, who had a declare office customary with the name “Douglas’ Mills”. A subsequent owner of the mill, Anthony Black, had the publicize of the post office misrepresented to “Multicaulisville”, after the mulberry tree (morus multicaulis), in which he had a financial concentration during a educational bubble in the tree. Lots were platted for sale in 1846 and the read out of the declare office was misused to “Blain”.

At one time, Blain was noted for bodily the smallest borough in Pennsylvania to own its own water reforest and electric street lighting system. Jacob Wentz was instrumental in the construction of the first water reforest in not quite 1869 or 1870. The borough was incorporated by an order of the Perry county court on November 3, 1877.

Blain is located at 40°20′14″N 77°30′38″W / 40.33722°N 77.51056°W / 40.33722; -77.51056 (40.337233, -77.510525).