The important contributions of female animators is slowly being uncovered by historians challenging traditionally held beliefs about early animation studios and those who worked in them.  For decades, the common belief was that these early animators, many of whom would come to work for Walt Disney, were only men.  This despite the evidence otherwise being right in front of their nose.  Animation historian Mindy Johnson came across an old illustration of animators from the 1920s.  Amongst the men was a woman.  When Johnson asked the owner of the illustration, a fellow animation historian, about the woman and whether she could have been an animator, he said he it was not likely and that he assumed that the woman was a cleaning lady or secretary.  He was very wrong—the woman was Bessie Mae Kelley, one of the earliest animators and directors of hand-drawn animated films. 

The Art Daily has an excellent article about Johnson’s research on Kelley and her contributions to animation:

Unfortunately, contributions by women and people of color are often forgotten because of the assumptions made by others.  Thankfully an historian who remembered a passing reference was willing to question the long-held assumption about the woman in the illustration and her role in early animation.