The area was first settled in 1804. The town of Portland was founded in 1813 from the town of Chautauqua. Subsequently, the town was reduced in size to form two new towns: Ripley (1816) and Westfield (1829).
A genealogical history of Portland was published in 1873 by Dr. H. C. Taylor, titled Historical Sketches of the Town of Portland, New York. An all names index was created for this book by Agnes Lee Mitchell in 1989 and published by the Chautauqua County Genealogical Society.