English: Region of Zaolzie in Czechia, historical borders based on "Zaolzie. Mapa turystyczna, Cieszyn, 2012, ISBN: 978-83-927052-7-7"; with Polish-speaking population from the 1910 census (File:Śląsk Cieszyński-Polacy 1910.png)
Yellow line - border of the Duchy of Teschen in the 16th century
Blue line - border from the 5th of November 1918
Purple line - Polish-Czech state border 1920-1938 and after 1945