Why is it called the Treasure Coast? The three coastal counties of Martin, St. Lucie & Indian River make up Florida’s Treasure Coast. During the 17th & 18th centuries Spanish galleons often were shipwrecked along this coastline as they traveled along Spain’s Ocean Trade Route. One of the most devastating losses for the Spanish treasure fleet was in 1715 when the Urca de Lima and ten other Spanish treasure ships were sunk by a hurricane off the coast of Ft. Pierce.