The Establishment Clause in the First Amendment to the United States Constitution provides that “Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof.” In applying the Establishment Clause to disputes ranging from prayer in schools and in state legislatures to monuments displaying the Ten Commandments or crosses on public grounds, the U.S. Supreme Court has acknowledged the strong role played by religion and religious traditions throughout our Nation's history—while recognizing that governmental intervention in religious matters can itself endanger religious freedom.

The Supreme Court described this balancing act: “Our institutions presuppose a Supreme Being, yet these institutions must not press religious observances upon their citizens. One face looks to the past in acknowledgment of our Nation's heritage, while the other looks to the present in demanding a separation between church and state. Reconciling these two faces requires that we neither abdicate our responsibility to maintain a division between church and state nor evince a hostility to religion by disabling the government from in some ways recognizing our religious heritage.”

In Missouri, as in all states, the Establishment Clause of the First Amendment to the U.S. Constitution prohibits the government from making any law 'respecting an establishment of religion, or prohibiting the free exercise thereof.' This means that Missouri's government cannot establish an official religion nor can it unduly interfere with the religious practices of its citizens. The U.S. Supreme Court has interpreted this clause to require a separation of church and state, but it has also recognized the historical role of religion in American life. In Missouri, this has led to legal cases involving religious displays on public property and prayer in public schools, among other issues. The courts have often used the 'Lemon test' (from the case Lemon v. Kurtzman) to determine whether a law or government action violates the Establishment Clause. This test considers whether the action has a secular purpose, whether its primary effect advances or inhibits religion, and whether it fosters an excessive government entanglement with religion. The balance sought is one that acknowledges religious heritage without promoting specific religious practices through government action.