Rainier III, Prince of Monaco Rainier III, Prince of Monaco Rainier III (Rainier Louis Henri Maxence Bertrand Grimaldi; 31 May 1923 – 6 April 2005) ruled the Principality of Monaco for almost 56 years, making him one of the longest ruling monarchs in European history. Though internationally known for his marriage to American actress Grace Kelly, he was also responsible for reforms to Monaco's constitution and for expanding the principality's economy beyond its traditional casino gambling base. Gambling accounts for only approximately three percent of the nation's annual revenue today; when Rainier ascended the throne in 1949, it accounted for more than 95 percent. Rainier
Monaco succession crisis of 1918 to one form or another of proximity of blood, and the Grimaldis' hitherto exclusive control of Monaco's dynastic marital policy was what threatened to enthrone a German duke on France's border, even after the Empire's defeat in war. Just as the ruling families of Britain, Russia, Belgium, and the Netherlands had all become patrilineally German by the twentieth century due to the propensity of monarchical heiresses, seeking dynastically equal marriages, to choose husbands from among Germany's many minor princely families, Monaco was on the verge of the same fate. Although the Grimaldis did not require inter-marriage with royalty by law