1926: Amos 'n' Andy debuts

History.com has this for 12 January about racism in radio:

On 12 January 1926, the two-man comedy series Sam ‘n’ Henry debuted on Chicago, Illinois’ WGN radio station. Two years later, after changing its name to Amos ‘n’ Andy, the show became one of the most popular radio programs in American history.
Though the creators and the stars of the new radio program, Freeman Gosden and Charles Carrell, were both white, the characters they played were two black men from the Deep South who had moved to Chicago to seek their fortunes. By that time, white actors performing in dark stage makeup or “blackface” had been a significant tradition in American theater for over a hundred years. Gosden and Carrell, both vaudeville performers, were doing a Chicago comedy act in blackface when an employee at the Chicago Tribune suggested they create a radio show.
When Sam ‘n’ Henry debuted in January of 1926, it became an immediate hit. In 1928, Gosden and Carrell took their act to a rival station, the Chicago Daily News’ WMAQ. When they discovered WGN owned the rights to their characters’ names, they simply changed them. As their new contract gave Gosden and Carrell the right to syndicate the program, the popularity of Amos‘n’Andy exploded. Over the next twenty years, the show would become the highest-rated comedy in radio history, attracting more than forty million listeners.
By 1951, when Amos'n’Andy came to television, changing attitudes about race and concerns about racism had virtually wiped out the practice of blackface. With Alvin Childress and Spencer Williams taking over for Gosden and Carrell, the show was the first television series to feature an all-black cast and the only one of its kind for the next twenty years. This did not stop African-American advocacy groups and eventually the National Association for the Advancement of Colored People (NAACP) from criticizing both the radio and television versions of Amos'n’Andy” for promoting racial stereotypes. These protests led to the television show’s cancellation in 1953.
The final radio broadcast of Amos'n’Andy aired on 25 November 1960. The following year, Gosden and Carrell created a short-lived televison sequel called Calvin and the Colonel. This time they avoided controversy by replacing the human characters with an animated fox and bear. The show was canceled after one season.

Rico says they were different times; now, of course, there are many all-black shows on television, some good, some bad...