From 1859 to 1877 , Romania evolved from a personal union of two vassal principalities ( Moldavia and Wallachia ) under a single prince to a full-fledged independent kingdom with a Hohenzollern monarchy .
From 1859 to 1877 , Romania evolved from a personal union of two vassal principalities ( Moldavia and Wallachia ) to a full-fledged independent kingdom .