Final answer:
The First Amendment to the U.S. Constitution grants citizens the right to free speech, along with freedoms of press, religion, assembly, and petition. The Fourteenth Amendment extends these protections to the states. Certain limitations exist to balance these freedoms with public safety and rights of others.
Step-by-step explanation:
The constitutional amendment giving United States citizens the right to free speech is the First Amendment. It not only secures the freedom of speech, but also the freedoms of press, religion, assembly, and petition. This amendment ensures that the federal government cannot pass laws that limit an individual's right to express opinions, particularly political speech. However, there are essential limitations to this right, including prohibitions against incitement to criminal activity, threats, and slander or libel.
Within the context of the states, the protection of these rights is extended through the Due Process Clause of the Fourteenth Amendment, as established in the case of Gitlow v. New York. Exceptions to these freedoms, as defined by the U.S. Supreme Court, serve to balance the rights of free expression with public safety and the rights of others.