Port St. Joe is a city located at the intersection of U.S. Highway 98 and State Road 71 in Gulf County, Florida, United States. As of the 2010 census the population was 3,445. This was a decline from 3,644 as of the 2000 census. Port St. Joe is the county seat of Gulf County.
St. Joseph was founded in 1835 by businessmen from nearby Apalachicola, which was troubled by legal conflict over land titles. It was mostly abandoned in 1841 after a yellow fever epidemic; a storm surge produced by a hurricane in 1844 destroyed what structures remained. In the early 20th century a new settlement was founded close to the original after the arrival of the Apalachicola Northern Railroad in 1909.