Which branch of government was not established by the US constitution?

The branch of government not explicitly established by the U.S. Constitution is the administrative state or the modern regulatory agencies. While the Constitution outlines the legislative, executive, and judicial branches, it does not detail the creation of various federal agencies that have developed over time to implement and enforce laws. These agencies, such as the Environmental Protection Agency (EPA) and the Securities and Exchange Commission (SEC), have evolved through legislative acts and executive orders rather than constitutional mandate.