Shortened from Wikipedia:

Dorothea Dix  was an American activist on behalf of the poor and insane who, through a program of lobbying state legislatures and Congress, created the first generation of American mental asylums.

She was made aware of the need for reform during a visit to Britain where she met reformers who were making great inroads on behalf of those suffering from mental illness.  After returning to America, Dorthea conducted a statewide investigation of care for the insane poor in Massachusetts. In most cases, towns contracted with local individuals to care for mentally ill people who could not care for themselves and lacked family/friends to do so. Unregulated and underfunded, this system resulted in widespread abuse.

In 1845, she successfully  she convinced the New Jersey legislature to authorize an asylum for the mentally ill, and many more states followed suit after a personal visit from Dorthea. She continued investigations in various northern states until the Civil War broke out and she was appointed Superintendent of Army Nurses by the Union Army, a position in which she served (often ) until August 1865. After the war ended, she focused her attention on crusading for the imprisoned, poor and mentally ill in the south.