Physical Characteristics. Martin County is north of the West Palm Beach-Boca Raton area and south of Ft. Pierce on the Atlantic Ocean. It is bordered by Okeechobee, St. Lucie, and Palm Beach counties. The county has 554.69 square miles of land and 123.80 square miles of water for a total of 678.49 square miles. The average January temperature is 65.1 degrees fahrenheit, and the average August temperature is 81.8 degrees fahrenheit. The average annual rainfall is 49.79 inches.
History. Martin County was established in 1925 from a portion of Palm Beach County and from a much smaller portion of St. Lucie County. The county was named for John W. Martin, governor from 1925 to 1929.
