Prologue was formed in 1982 to offer residential support services in Baltimore County to persons with serious and persistent mental illness. In 1987, homeless outreach services began with Prologue case managers reaching out to people in the Baltimore County Detention Center and shelters. In 1989, Springfield Hospital patients who had been hospitalized ten years or more began to transition to community-based services offered by Prologue in Carroll County. The Drop-In Center opened its doors in 1994 on evenings and weekends to offer community peer support to persons recovering from mental illness.

Today Prologue continues to focus on community based personal recovery.