The Eastern Maine Insane Hospital was opened on July 1, 1901. Within five days of opening, 145 patients were transferred from the Maine Insane Hospital in Augusta to the Bangor location. Patients were generally committed to the hospital by their community peers, such as town selectmen, family, etc.

Patients worked the fields, raised livestock, manned the laundry, sewing room and kitchen as part of their "treatment." This made the hospital self-sufficient and any excesses were sold at market to pay additional costs, until 1973 when the case of Sonder vs. Brennan went to court and it was determined that patients in public institutions could not work without being paid.

The name of the hospital changed in 1913 to Bangor State Hospital and then eventually to Bangor Mental Health Institute in the early 1970s. The highest patient census was in 1970 with 1,200 patients; however, with a concerted downsizing effort, the census fell to 470 in 1974. There were approximately 300 patients through much of the 1980s.

Treatment for patients ranged from 'family' type care in the early 1900s to hydrotherapy and electrical therapies in the 1930s. The hydrotherapy and electrical therapies, however, were only used for a small number of patients. Most patients, who were thought to be incurable, received little specific treatment for their problems. New effective medications for mental illness became available in the mid-1950s. On August 26, 2005 the BMHI name was changed to Dorothea Dix Psychiatric Center.