Port Allen is a city in, and the parish seat of, West Baton Rouge Parish, Louisiana, United States. Port Allen is located between Interstate 10 and US Highway 190 on the west bank of the Mississippi River. The population was 5,180 at the 2010 census, down from 5,278 in 2000. It is part of the Baton Rouge Metropolitan Statistical Area.Port Allen is home to the Mississippi Riverfront Development, which provides a panoramic view of the Mississippi River and Baton Rouge, the West Baton Rouge Museum, the City of Port Allen Railroad Depot, Scott's Cemetery, the Port of Greater Baton Rouge, the Port Allen Lock.Port Allen is named for Governor Henry Watkins Allen.