The historical regions of Romania are located in Central, Southeastern, and Eastern Europe. Romania came into being through the unification of two principalities, Wallachia and Moldavia in 1862. The new unitary state extended over further regions at various times during the late 19th and 20th centuries, including Dobruja in 1878, and Transylvania in 1918. These regions are part of Romania today:
1. Banat: since 1918 divided between Romania, Kingdom of Serbs, Croats and Slovenes (today Serbia) and Hungary.
2. Crisana: the region bordered by the rivers Mures and Somes and the Apuseni Mountains following the declaration of the union in 1918.
3. Maramures: the mountainous northwestern region following the declaration of the union in 1918.
Between 1918-1920, during the Revolutions and interventions in Hungary the Hungarian–Romanian War effected also part of these territories until the final resolution of state affairs by the Paris Peace Conference.
4. Transylvania: (the term sometimes encompasses not only Transylvania proper, but also part of the historical regions of Crisana, Maramures, and Banat. The new borders were set by the Treaty of Trianon in 1920 between the respective states).
5. Oltenia (Lesser Wallachia): the territory between the rivers Danube and Olt and the Southern Carpathian became part of the Principality of Wallachia in the early 14th century.
6. Wallachia: Muntenia (Greater Wallachia): part of Wallachia (which united with Moldavia in 1859 to create modern Romania).
7. Dobruja (Northern Dobruja): in Romania since 1878 (excepting some Danubian islands and the Snake Island which were incorporated in the USSR in 1948, and became part of Ukraine since 1991).
8. Moldavia (Western Moldavia): part of Moldavia (which united with Wallachia in 1859 to create modern Romania).
9. Bukovina: in Romania between 1918 and World War II, today divided between Romania and Ukraine.