How were people with developmental delays treated, especially during the 1900s-1950s?

In the years of 1900 - 1950’s, the people with developmental disabilities were not treated well throughout the years. If the new born baby has a developmental delay they will be treated like slaves, abused the baby and also make fun of. The parents of the child who had that developmental delay created a movement for a better life for people with developmental delays around 1950.