Please answer a question about the following article about Law of the United States:

The law of the United States comprises many levels of codified and uncodified forms of law, of which the most important is the United States Constitution, the foundation of the federal government of the United States. The Constitution sets out the boundaries of federal law, which consists of acts of Congress, treaties ratified by the Senate, regulations promulgated by the executive branch, and case law originating from the federal judiciary. The United States Code is the official compilation and codification of general and permanent federal statutory law.

What is the foundation of the United States federal government?
United States Constitution