Massachusetts is a state.   In fact, from 1776 to 1780, Massachusetts was officially designated the “State of Massachusetts Bay.”   So why did Massachusetts start calling itself a commonwealth?

The short answer is that the second draft of the Massachusetts Constitution, which was adopted in 1780, states “that the people . . . form themselves into a free, sovereign, and independent body politic, or state by the name of The Commonwealth of Massachusetts.”  At that point, Massachusetts legally became a commonwealth.

The longer answer is more interesting.  The word “commonwealth” started life in 15th century England, when the word “wealth” included the meaning “weal” or “well-being.”  To speak of  “the commonwealth” in those days was to invoke the abstract idea of a common or general good.  By the late 18th century, however, the word “commonwealth” had become somewhat radical and cool, because it was associated with the idea of political power being rooted in the people rather than the king.   A “commonwealth” was a state in which the common good was associated with common power.   A “commonwealth” was understood by educated people as a republic, or as any political entity in which sovereignty belonged to the people.

Massachusetts adopted the designation of commonwealth in 1780 to underscore that it was now a self-governing republic with no allegiance to the king.