It began in 1953 when thorazine was introduced on the premise that it would allow previously institutionalized people to live normal lives with only outpatient care. This turbocharged the movement to shutter mental institutions, and their populations began to crater around 1956. [0] For a lot of people, thorazine and its descendants have been nothing short of miraculous and have lived up to the promise. But not for everyone, and in the name of charity and respect for individual autonomy, we have chosen to allow these people to either live in awful conditions and fend for themselves or do something prison-worthy. So, while there isn’t great data on homelessness from before the 21st century, the root cause of much of it - a societal refusal to recognize certain people as requiring lifelong care for mental illness - begins in 1953. [0] https://chicagounbound.uchicago.edu/cgi/viewcontent.cgi?refe...