Answer:
the Declaration of Independence
Explanation:
The American Revolutionary War was a war of independence of the United States of America that was fought between the 19th of April, 1775 and 3rd of September, 1783. The war started when the delegates from the thirteen (13) American colonies in Congress (First continental congress) revolted against the Great Britain over their lack of representation in the colonies and refusal to give consent to parliament's taxation such as Stamp Act and Townshend Acts.
The Declaration of Independence was written by President Thomas Jefferson to record the proclamation of the Second Continental Congress which declared American Colonies free from Great Britain.
Basically, the Declaration of Independence is a public Act through which the American Colonies were legally declared free from Great Britain by the Second Continental Congress on the 4th of July, 1776. It was signed by the 56 delegates at the Second Continental Congress.
Hence, the foundational document which was written during the build-up to the Revolutionary War is the Declaration of Independence.
