Which state constitution, adopted in 1780, is the oldest functioning written constitution in the world?

The Massachusetts Constitution, adopted in 1780, is the oldest functioning written constitution in the world.

Massachusetts voters ratified the constitution on June 15, 1780, during the American Revolutionary War. John Adams drafted much of the document and later described its structure as creating separate legislative, executive, and judicial powers.

The constitution established a framework of government for Massachusetts that remains in force, although it has been amended many times. Its declaration of rights and separation of powers influenced later American constitutional design.

It predates the United States Constitution by seven years. The Massachusetts document is not the oldest constitution ever written, but its continuing operation is what gives it the distinction of being the oldest functioning written constitution.