Luther Emmett Holt wrote a book called “The Care and Feeding of Children”, in 1884 . In his book he talked about “airing out children”, or simply put, providing children with fresh air. Busy parents took a shortcut and purchased cages for the children to sit in outside of high rises and tall apartment buildings rather than actual walks in the park or strolls down the street.
So on any given day you could see babies hung out windows over busy streets without a safety care in the world.
FYI: The cages were invented in the United States in 1922 but took off big time in London.