Final answer:
The document that became America's first national constitution was The Articles of Confederation. However, it was replaced by the United States Constitution in 1787.
Step-by-step explanation:
The document that became America's first national constitution was The Articles of Confederation. The Articles of Confederation were drafted in 1776-1777 and ratified by the thirteen colonies in 1781. However, the Articles of Confederation had several shortcomings, leading to the drafting and adoption of the United States Constitution in 1787, which replaced the Articles of Confederation and significantly strengthened the central governmental authority of the country.
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