High Quality Content by WIKIPEDIA articles! The St. Johns River Light is a decommissioned lighthouse in Jacksonville, Florida, U.S., which formerly marked the mouth of the St. Johns River. It is located on the grounds of Naval Station Mayport in the Mayport area. Constructed in 1858, it was decommissioned in 1929 and replaced with a lightship. It is sometimes known as the "Old St. Johns River Light" to distinguish it from the modern St. Johns Light, built in 1954.