What document established the three branches of the federal government?

The Constitution is the foundational document that established the three branches of the federal government: the legislative, executive, and judicial branches. It was drafted in 1787 and outlines the framework for the organization, powers, and responsibilities of each branch in Articles I, II, and III respectively.

The structure created by the Constitution is critical in defining the separation of powers, which is a fundamental principle in American governance. This system is designed to prevent any one branch from becoming too powerful by allowing each branch to have distinct responsibilities and the ability to check the powers of the others.

The other options—such as the 14th and 18th Amendments and the Bill of Rights—do not establish the branches of government. Instead, the amendments modify specific aspects of governance or individual rights, while the Bill of Rights specifically details protections for individuals against government overreach, emerging as the first ten amendments to the Constitution. Hence, the Constitution serves as the essential document that laid the groundwork for the structure of the federal government.