The First Amendment to our Constitution was ratified in 1791, in which it states in part: “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof.” This Amendment was essentially the first of its kind in any written Constitution, for it took away the possibility of the power of a coerced religion established by our national government to rule over the people, but instead made the commitment that the national government would not established any religion upon the people, and that, the people, themselves, had the right to freely exercise their own volition in regards to their religious preference.
At the time of this Amendment, there were several States of the Union that had within their own State, an established religion, such as Anglican in Virginia and New York, and Congregational in Massachusetts, but there were also States that had no established religion such as Georgia, Pennsylvania, and New Jersey. Though some of these States did have an established religion, such a religion was not national in scale, and all of these States eventually dropped such, in which after the passage of the Fourteenth Amendment, the validity of an established religion within a respective State was null and void.
What made the proclamation that this country would not establish a national religion, so special and so profound for its time, was first off, England, itself, had an established state religion, as well as most other European countries had essentially merged the power of the state with the power of religion, so that the people were effectively under the hand of a combination of state and church, which saw them as subjects to be controlled rather than as free people to be liberated in their lives and viewpoints.
The United States believed that when it came to religious liberty, that the most important part of such was for the individual to be able to make their own choice of whatever religious faith that they so desired, or even, to have no faith, not because America believed that religion was bad for people, but because America believed that to compel people to have a certain faith as dictated by the power of the national government, was a violation of one's freedom of choice, one's freedom of belief, and one's freedom of exercise to believe or disbelieve in whatever Higher Power that a given individual gravitated to, for that belief or unbelief is an individual matter between that person and his Creator, and not therefore something that the national government should infringe upon.
The greatest value of this non-establishment of a national religion is that America, more than any other nation, openly embraces the free exercise of an individual's choice of religion, which has allowed this nation to openly embrace faiths of all different flavors within this great country, which is why America has such a great diversity of faith, but also such a great diversity of people, so that it is truly a melting pot of different people, of different cultures, and of different faiths, that are joined together under a national Constitution that permits all people to have liberty and to pursue their own happiness for the good and betterment of those same people.