From The Jim Crow Museum by the Ferris State University
This is the most well-known and enduring caricature of African American women. During slavery, it was proof to naysayers that black women at least were content, happy even, as slaves. This caricature showed an obese, coarse, maternal figure. She was thought to be completely desexualized even though she had kids of her own. She was property of the white family. She was the right hand of the slavery master's wives. After slavery, she was the nanny and the maid. She was made to be extremely dark, "ugly", and old/middle-aged since their light-skinned counterpart was the mainstream definition of female sexual attractiveness. This was to desexualize the mammy because no white man would choose the mammy over a white woman of any kind. This de-eroticism of mammy meant that the white wife was safe meaning the white family was safe.