The area has been populated by Slavic peoples since at least the 7th century. According to the legend, in 810 three sons of a prince – Bolko, Leszko and Cieszko, met here after a long pilgrimage, found a spring, and decided to found a new settlement. They called it Cieszyn, from the words "cieszym się", "I'm happy". This well can be found at the ulica Trzech Braci ("Three Brothers Street"), just west of the town square.

The town was the capital of the Duchy of Teschen and shared its history throughout the ages. It was in Teschen where Maria Theresa and Frederick II signed on 13 May 1779, the Teschen Peace Treaty, which put an end to the War of the Bavarian Succession. Teschen was known for its national, religious and cultural diversity, comprising mostly of German, Polish, Jewish and Czech communities. There was also a small but lively Hungarian community in the town comprised mostly of officers and clerks.

According to the Austrian census of 1910 the town had 22,489 inhabitants. 13,254 (61.5%) were German-speaking, 6,832 (31.7%) were Polish-speaking and 1,437 (6.7%) were Czech-speaking. Jews were not allowed to declare Yiddish, most of them thus declared German as their native language. The most populous religious groups were Roman Catholics with 15,138 (67.3%), followed by Protestants with 5,174 (23%) and the Jews with 2,112 (9.4%).

The town was divided in July 1920, by the Spa Conference, a body formed by the Versailles Treaty, leaving a sizeable Polish community on the Czechoslovak side. Its smaller westerns suburbs became what is now the town of Český Těšín in the Czech Republic. Both towns were joined together again in October 1938 when Poland annexed the Zaolzie area together with Český Těšín. In 1939 whole Cieszyn Silesia was annexed by German forces and during the World War II was a part of Nazi Germany. After the war, the border between Poland and Czechoslovakia was restored to the one from 1920.

After Poland and the Czech Republic joined the European Union and its passport-free Schengen zone, border controls were abolished and residents of both the Polish and Czech part can move freely across the border.

source www.en.wikipedia.org