What dialect did Leo Rosten explore?

Leo Rosten was most famous for exploring the Yiddish language in his writing and research. He was a scholar of Yiddish and wrote several books on the topic, including:

* The Joys of Yiddish (1968): A humorous and insightful exploration of the language, its history, and its impact on American culture.

* The Meaning of Yiddish (1969): A more academic study of the language's origins, structure, and evolution.

* The H₂O of Yiddish (1982): A collection of essays and articles on various aspects of Yiddish culture and language.

He also created the fictional character "H.L. Mencken" (not to be confused with the real H.L. Mencken), who was a Yiddish-speaking columnist in the fictional town of "Carmel, California" (also a fictional place created by Rosten). This character allowed Rosten to explore the humor and wisdom of Yiddish in a light-hearted way.

So while Rosten explored many aspects of American culture, Yiddish was his main focus, and he is considered one of the leading experts on the language and its place in history.