I've been trying to verify the following with more information, but it seems accurate.
21 April 1937, New York Herald Tribune, pg. 20, col. 1:
Gus Hill Dead;
In the Theater
Minstrelsy was in its heyday then and the combination entertainment known as "variety" was yet to be born in this country. "Variety," according to Mr. Hill, first appeared at Broadway and Grand Street when an English actor refused to do his work in blackface as a part of a minstrel show, and insisted that his act be added instead as a specialty.