The history of First Parish in Lexington extends back to the late 17^th century, when residents of Lexington, then called Cambridge Farms, repeatedly sent petitions to the Massachusetts Legislature asking to establish their own parish. The state finally acquiesced to their petition in 1691 and five years later, the church was finally established - Calvinist in doctrine, congregational in polity. In 1829, the parish voted to become Unitarian.

Today, the church is a self-governing, liberal congregation that works with a professional staff, offering religious education, events and activities.