The story starts a few years before the building. In 1804, a group called the Religious Improvement Society began meeting weekly for lectures and prayer. On February 27, 1809, that society organized itself as a church. Park Street Church describes its founders as a group of 26 men and women, gathered during what it calls the Unitarian wave of the early nineteenth century. They were committed to Trinitarian teaching and to congregational governance, which means each congregation runs its own affairs. The National Park Service puts it this way: the church was organized in reaction to Unitarians who were gaining control of many of the old Puritan churches. So this corner began as a statement of belief in a city where religious ground was shifting. The first pastor was Edward Dorr Griffin, who preached a famous series of Sunday evening sermons. Just a few years later, in 1816, Park Street joined with Old South Church to form the City Mission Society, a social service society for Boston's urban poor. Even in its early years, the congregation paired doctrine with outreach.