Prince Rainier III, born on May 31, 1923, succeeded his grandfather, Louis II, on the latter's death, on May 9, 1949. Rainier was married, in 1956, to American actress Grace Kelly and they subsequently had three children. Their son, Prince Albert Louis Pierre (b. 1958) was heir to the throne. Immensely popular, Princess Grace died on Sept. 14, 1982, of injuries sustained in a car accident near Monte Carlo. She was 52.