By that time he had been in show business 50 years, and was an African American entertainment institution as well as an occasional face in the mainstream (chiefly on Ed Sullivan).
Markham started out in carnivals as a teenager in native Durham, North Carolina, then graduated to all-black minstrel shows, black vaudeville and white burlesque, then films, record albums and television, He was to wear blackface until the 1940s, a common practice at the time, even among African Americans, although he was one of the last hold-outs and defenders of the practice, citing the usefulness of the burnt cork as a comic mask. But times changed and he changed with them. Markham became a major fixture at the Apollo Theater in his later years. He passed away in 1981.
To learn more about vaudeville, including great comedians like Pigmeat Markham, consult No Applause, Just Throw Money: The Book That Made Vaudeville Famous, available at Amazon, Barnes and Noble, and wherever nutty books are sold.