The term "United Principalities" refers to the historical union of the principalities of Moldavia and Wallachia in the mid-19th century. This union was formalized in 1859 when Alexandru Ioan Cuza was elected as the ruler of both regions, marking a significant step towards the eventual formation of modern Romania. The United Principalities aimed to strengthen the political and economic ties between the two regions, which had shared cultural and historical backgrounds. This union laid the groundwork for the unification of Romania in 1866, further solidifying the identity and governance of the Romanian state.