Brian, Sam Cowell 1820-1864 was among the first Music-hall performers (possibly the first depending on how you define the term Music-hall). He was born in England into an acting family. Raised in America from the age of two. His wife wrote a wonderful biography spanning the time of their tour in America. It's worth reading. "The Cowells in America. 1860 - 1861" with an introduction by Wilson Disher.
Tell you what, though. I wrote a chapter (and quite a bit more) about him in my study of the Billy Barlow phenomenon. You can find it at as an e-book. It's called "Hey Ho Rageddy-o. A Study of the Billy Barlow Phenomenon".
Cheers, Joy