Transylvania as originally defined in Treaty of Trianon, 27 years earlier, thus confirming the return of Northern Transylvania to Romania. From 1947 to 1989, Transylvania, along with the rest of Romania, was under a communist regime. The ethnic clashes of Târgu Mureș occurred between ethnic Romanians and Hungarians in March 1990 after the fall of the communist regime and became most notable inter-ethnic incident in the post-communist era. The Transylvanian Plateau, high, is drained by the Mureș, Someș, Criș, and Olt rivers, as well as other tributaries of the Danube. This core of historical Transylvania roughly corresponds with nine counties of
Transylvania to Transylvania, and 280,000 from Transylvania to the Old Kingdom, most notably to Bucharest). According to the results of the 2011 Population Census, the total population of Transylvania was 6,789,250 inhabitants and the ethnic groups were: Romanians - 70.62%, Hungarians - 17.92%, Roma - 3.99%, Ukrainians - 0.63%, Germans - 0.49%, other - 0.77%. Some 378,298 inhabitants (5.58%) have not declared their ethnicity. The presented data are from http://www.recensamantromania.ro/rezultate-2, the Table no. 7. The ethnic Hungarian population of Transylvania form a majority in the counties of Covasna (73.6%) and Harghita (84.8%). The Hungarians are also numerous in the following counties: