In the late 1800s, the city of Bia?ystok – which was once Polish, then Prussian, then Russian, and is today again part of Poland – was a hub of diversity, with large numbers of Poles, Germans, Russians and Yiddish-speaking Ashkanazi Jews. Each group spoke a different language and viewed members of the other communities with suspicion. For years, L.L. Zamenhof – a Jewish man from Bia?ystok who had trained as a doctor in Moscow – had dreamed of a way for diverse groups of people to communicate easily and peacefully. On July 26, 1887, he published what is now referred...