The first three articles of the U.S Constitution mention the following:
Article I: The legislative power of the government is established, where the House of Representatives and the Senate are included, as well as the forms of election and the powers that this power has.
Article II: The executive power is described, which es represented by the presidency, the selection processes, requirements for this to begin his position, the oath that he must render and the duties that he must carry out in the office.
Article III: The judicial system is mentioned, where the Supreme Court of the United States is included.