Blurb:

The only proposal of an international language that had lasting success was Esperanto, invented in Poland in the late nineteenth century by Ludwig Zamenhof. It was created in 1887, got a boost in popularity in the 1920s and even became a candidate to be the official language of the League of Nations. Esperanto is by far the most successful language in the long history of language invention. It isn’t a universal language, and it’s unlikely to become one, but it has become a living language.