  thumb|250px|polish map of cieszyn silesia. the solid black line is the historical border of the region, and the broken black line is the international border. thumb|250px|map of cieszyn silesia and its polish-czech historical borders in 1918-1945 cieszyn silesia or tÄÅ¡Ã­n silesia or teschen silesia (, polish: , czech:  or , german: teschener schlesien or olsagebiet) is a historical region in south-eastern silesia, centered on the towns of cieszyn and ÄeskÃ½ tÄÅ¡Ã­n and bisected by the olza river. since 1920 it has been divided between poland and czechoslovakia, and later the czech republic. it covers an area of about  and has about 810,000 inhabitants, of which  (44%) is in poland, while  (56%) is in the czech republic. the historical boundaries of the region are identical to those of the former independent duchy of teschen/cieszyn. currently, most of cieszyn silesia forms one of the euroregions, the cieszyn silesia euroregion. == administrative division == from an administrative point of view, the polish part of cieszyn silesia lies within the silesian voivodeship and comprises cieszyn county, the western part of bielsko county, and the western part of the town of bielsko-biaÅa. the czech part lies within the moravian-silesian region and comprises the karvinÃ¡ district, the eastern part of the frÃ½dek-mÃ­stek district, and the eastern parts of the ostrava-city district and of the city of ostrava itself. == history == thumb|200px|piast tower in cieszyn    cieszyn silesia covers the area of the former duchy of teschen, which existed from 1290 to 1918. before 1290 the area constituted a castellany, which together with castellany of racibÃ³rz formed the duchy of racibÃ³rz in 1172. from 1202 it was a part of the united duchy of opole and racibÃ³rz. from 1290 to 1653 the duchy of teschen was ruled by the local branch of the piast dynasty. in 1327 casimir i, duke of cieszyn, swore homage to the bohemian king john of bohemia, and the duchy became an autonomous fiefdom of the kingdom of bohemia and later the bohemian crown. piast rule continued until 165
Cieszyn_Silesia Czech_RepublicaPoland_border Territorial_disputes_of_Czechoslovakia Territorial_disputes_of_Poland