Grace Kelly was the first American to marry a reigning Prince of Monaco. Is that true or false?

False - that distinction belongs to Alice Heine. She was born Marie Alice Heine (February 10, 1858 – December 22, 1925) at 900 Rue Royale, in the French Quarter of New Orleans, Louisiana. The American Civil War sent the family to France, where the teenaged Alice's beauty and her family's wealth, made a great impression in Parisian society.

Alice's second marriage, to Prince Albert I of Monaco, Sovereign Prince of Monaco, occurred on October 30, 1889. Heine, as Albert's second wife, was then styled HSH The Princess of Monaco. Prince Albert I was the great-grandfather of Prince Rainier III of Monaco.

Prince Rainier married Oscar-winning American actress Grace Patricia Kelly only in 1956. The 26-years old actress retired from acting and began her duties as Princess of Monaco. They had three children.