On this date in 1791 the first 10 amendments — known as the Bill of Rights — were ratified by the states of the new United States.
The National Archives has a page dedicated to the Bill of Rights.
And just as a reminder, the First Amendment of the Bill of Rights is as follows:
Amendment I
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.