Abandonment increased towards the end of the 19th century, particularly in the United States. The largest migration of abandoned children in history took place in the United States between 1853 and 1929. Over one hundred and twenty thousand orphans (not all of whom were intentionally abandoned) were shipped west on railroad cars, where families agreed to foster the children in exchange for their use as farmhands, household workers, etc. Orphan trains were highly popular as a source of free labor. The sheer size of the displacement as well as complications and exploitation that occurred gave rise to new agencies and a series of laws that promoted adoption rather than indenture. By 1945, adoption was formulated as a legal act with consideration of the child’s best interests. The origin of the move toward secrecy and the sealing of all adoption and birth records began when Charles Loring Brace introduced the concept to prevent children from the orphan trains from returning to or being reclaimed by their parents.