Jupiter Islan is a town on the barrier island of Jupiter Island in Martin County, Florida, United States. The population was 620 at the 2000 census. As of 2004, the population recorded by the U.S. Census Bureau is 653 . Some of the wealthiest people in the United States live in Jupiter Island's closed community, which ranks 2nd on the list of the highest-income places in the country. Mail delivery is from the Hobe Sound post office and many town residents when away from the area will say they are from Hobe Sound.