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The Accession of Prince Rainier III of Monaco on this day in 1949, after the death of his grandfather, Prince Louis II. The new sovereign Prince (wearing the Order of Saint-Charles) of the small Mediterranean Principality was joined by his parents, Princess Charlotte and Prince Pierre, step-grandmother Princess Ghislaine, and sister Princess Antoinette for the Inauguration Mass at Saint Nicholas Cathedral in Monte Carlo. Prince Rainier, who was the son of Prince Louis’s legitimized daughter, Princess Charlotte, famously married actress Grace Kelly, and reigned for 56 years until his death in 2005.