Jupiter's name goes back to the Hobe people who lived at the mouth of the Loxahatchee River. A mapmaker recorded the Spanish spelling Jobe as Jove, and later mapmakers took that for the Roman god Jupiter. Nearby Juno Beach was named in turn for Jupiter's consort.
More about Jupiter
On January 24, 1838, during the Second Seminole War, Major General Thomas S. Jesup led about 1,500 men against roughly 300 Seminoles at the headwaters of the Loxahatchee. Jesup was shot in the face, seven soldiers were killed and 31 wounded, and the Seminoles withdrew into the Everglades. The Jupiter Inlet Lighthouse was finished in 1860 and painted red in 1910.
The narrow-gauge Jupiter and Lake Worth Railway opened on July 4, 1889, running 7.5 miles from Jupiter to Juno. In 1893 Harper's magazine called it the "Celestial Railroad" because it stopped at Jupiter, Mars, Venus and Juno. It closed in April 1895. Harry and Susan DuBois built their home on a Native American mound in 1898, and it is one of the oldest surviving houses in the county.
Sources
Wikipedia: Jupiter, Florida
The Historical Marker Database: Jesup's Battle; The Jupiter and Lake Worth Railway; DuBois Pioneer Home