Oath of Fidelity and Support
The Province of Maryland was a colony of Great Britain from 1632 until 1776, where Maryland declared itself a sovereign state as one of the Thirteen Colonies declaring independence from Great Britain. The Thirteen Colonies came together to sign the United States Declaration of Independence (the founding document of the United States), which outlined why the United States of America would no longer be subject to British rule and that the Thirteen Colonies would be regarding themselves as sovereign states.
Source: Wikipedia — Oath of Fidelity and Support (CC BY-SA 4.0)