Mayport is a small community located between Naval Station Mayport and the St. Johns River in Jacksonville, Florida. It is part of the Jacksonville Beaches communities on San Pablo Island. The only public road to Mayport is State Road A1A, which crosses the St. Johns River Ferry to Fort George Island. On June 3, 1909, through action of the state legiā¦Mayport is a small community located between Naval Station Mayport and the St. Johns River in Jacksonville, Florida. It is part of the Jacksonville Beaches communities on San Pablo Island. The only public road to Mayport is State Road A1A, which crosses the St. Johns River Ferry to Fort George Island. On June 3, 1909, through action of the state legislature, Mayport was incorporated as a city.