On December 5, 1835 it was ordered by the Board of Commissioners "that the County Seat of Jay County be designated and known by the name of Portland." By the act of the Indiana Legislature, the town was incorporated on January 25, 1843. It was incorporated as a city in 1883.

The central business district of Portland was placed on the National Register of Historic Places in 1996. Included within the district are the bowstring truss bridge and the Jay County Courthouse. Also the National Register is Floral Hall located at the Jay County Fairgrounds.