The Bill of Rights went into effect in 1791. It made 10 amendments to the U.S. Constitution, which was signed in 1787.
The First Amendment states:

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.

One of the best websites on the internet for discussion and study of First Amendment matters — particularly the freedom of the press — is the First Amendment Center.