In 1715, several Spanish ships loaded with treasure (known as the 1715 Treasure Fleet) encountered a storm off the shores of the Treasure Coast and were lost. It is estimated that only a portion of the sunken treasure has been found. The value placed on the treasure lost from the 1715 fleet has been estimated at more than $500 million.
The town of Sebastian was a fishing village as early as the 1870s. In the early 1880s David Peter Gibson and Thomas New settled in the area. New filed to start a post office under the name New Haven. However, New got into legal trouble for misuse of his position as postmaster and was removed. Officially, Sebastian was founded in 1882 and named St. Sebastian, after Saint Sebastian