The main reasons for children being adopted in the United Kingdom had been unmarried mothers giving up their children for adoption and stepparents adopting their new partners children". United States
In the United States, foster care started as a result of the efforts of Charles Loring Brace. "In the mid 19th Century, some 30,000 homeless or neglected children lived in the New York City streets and slums." Brace took these children off the streets and placed them with families in most states in the country. Brace believed the children would do best with a Christian farm family. He did this to save them from "a lifetime of suffering" He sent these children to families by train, which gave the name The Orphan Train Movement. "This lasted from 1853 to the early 1890s  and transported more than 120,000 250,000? children to new lives." When Brace died in 1890, his sons took over his work of the Childrens Aid Society until they retired. The Childrens Aid Society created "a foster care approach that became the basis for the federal Adoption and Safe Families Act of 1997" called Concurrent Planning. This greatly impacted the foster care system.
In a research study conducted at the University of Minnesota, researchers found that children placed in non-parental homes, such as foster homes, showed significant behavior problems and higher levels of internalizing problems in comparison to children in traditional families and even children who were mistreated by caregivers. According to an article written by Elizabeth Curry titled The five things you should know about how orphanage life affects children  they state that a child who has lived in an orphanage or a home for multiple children, they will have learned survival skills but lack family skills due to them never understanding permanency. Medical and psychiatric disorders
A higher prevalence of physical, psychological, cognitive and epigenetic disorders for children in foster care has been established in studies in various countries. The Casey Family Programs Northwest Foster Care Alumni Study was a fairly extensive study of various aspects of children who had been in foster care. Individuals who were in foster care experience higher rates of physical and psychiatric morbidity than the general population and suffer from not being able to trust and that can lead to placements breaking down.In the Casey study of foster children in Oregon and Washington state, they were found to have double the incidence of depression, 20% as compared to 10% and were found to have a higher rate of posttraumatic stress disorder (PTSD) than combat veterans with 25% of those studied having PTSD.