Foster Care was around in sort as early as the mid 1500's.
Children were placed into homes where they could earn their keep as indentured servants. The document I've read said that this was a positive, got the children out of almshouses where they were unprotected from the unthinkable.
In the mid-1800's New York Children's Aid Society was created due to the number of immigrant children on the streets. From there other states began to adopt their own versions of foster care.
Reunification of biological families is the end goal of foster care. There are issues that can void this goal. If a parent has killed another one of their children. Extreme abuse. Commission of a felony that resulted in injury to the child. Another big one, a registered sex offender (but only in three states).
When I expressed concern over the psyches, the emotional upheaval of the children in our life, when their biological parents behaved badly, a social worker told me something pretty horrific. She said that the emotional well-being of the child is not part of the reunification goal. Imminent danger is the only consideration. Poor parenting, semi-neglect, indifference, lack, none of those are issues that derail the reunification process.
to be continued...