Not perpetual, but the Articles of Confederation established a union that could only be broken by approval of Congress with ratification by all the state legislatures.
Although this is pre-Constitution, it does matter because Article 6 of the Constitution states: “All Debts contracted and Engagements entered into, before the Adoption of this Constitution, shall be as valid against the United States under this Constitution, as under the Confederation.”
Even the very creation and adoption of the Constitution was not according to the rules set up in the Articles—rather created by the Constitutional Convention. If one tiny clause in the Articles are all one has to base keeping in union about, that’s shakey ground indeed!
That would also exempt subsequent states, outside of the original 13, from any imagined commitment to union.
"Although this is pre-Constitution, it does matter because Article 6 of the Constitution states:
'All Debts contracted and Engagements entered into, before the Adoption of this Constitution, shall be as valid against the United States under this Constitution, as under the Confederation.' "
This bears repeating.
The old Articles of Confederation were explicitly "perpetual," as stated in the preamble, and again in:
"Article XIII. Every State shall abide by the determination of the united States in congress assembled, on all questions which by this confederation are submitted to them.And the Articles of this confederation shall be inviolably observed by every State, and the union shall be perpetual; nor shall any alteration at any time hereafter be made in any of them; unless such alteration be agreed to in a congress of the united States, and be afterwards confirmed by the legislatures of every State."