Concerning the First Amendment

Joseph Story was an early Supreme Court justice.  His Commentaries on the Constitution of the United States have been cited repeatedly by the Supreme Court.   There are 172 citations in federal court decisions since 2021.  Concerning freedom of religion, let me quote from there:

1877. The real object of the [First] amendment was not to countenance, much less to advance, Mahometanism, or Judaism;, or infidelity, by prostrating Christianity; but to exclude all rivalry among Christian sects, and to prevent any national ecclesiastical establishment which should give to a hierarchy the exclusive patronage of the national government. [2 Story, Commentaries on the Constitution of the United States 606 (1873).

If you examine the laws of the early Republic, you will see that this appears repeatedly.  The dominance of Christianity was simply assumed.  The Pennsylvania Constitution of 1776, section 10, includes this requirement for officeholders:

And each member, before he takes his seat, shall make and subscribe the following declaration, viz:

I do believe in one God, the creator and governor of the universe, the rewarder of the good and the punisher of the wicked. And I do acknowledge the Scriptures of the Old and New Testament to be given by Divine inspiration.

And no further or other religious test shall ever hereafter be required of any civil officer or magistrate in this State.

From the North Carolina Constitution of 1776:

That no person, who shall deny the being of God or the truth of the Protestant religion, or the divine authority either of the Old or New Testaments, or who shall hold religious principles incompatible with the freedom and safety of the State, shall be capable of holding any office or place of trust or profit in the civil department within this State.

 The South Carolina Constitution of 1778, Article III:

III. That as soon as may be after the first meeting of the senate and house of representatives, and at every first meeting of the senate and house of representatives thereafter, to be elected by virtue of this constitution, they shall jointly in the house of representatives choose by ballot from among themselves or from the people at large a governor and commander-in-chief, a lieutenant-governor, both to continue for two years, and a privy council, all of the Protestant religion, and till such choice shall be made the former president or governor and commander-in-chief, and vice-president or lieutenant-governor, as the case may be, and privy council, shall continue to act as such.

Article XII defines the qualifications of state senators:

 [N]o person shall be eligible to a seat in the said senate unless he be of the Protestant religion, and hath attained the age of thirty years, and hath been a resident in this State at least five years.

Article XIII defines the requirements to be an elector for the General Assembly, and to be elected to the General Assembly:

The qualification of electors shall be that every free white man, and no other person, who acknowledges the being of a God, and believes in a future state of rewards and punishments, and who has attained to the age of one and twenty years.... No person shall be eligible to sit in the house of representatives unless he be of the Protestant religion, and hath been a resident in this State for three years previous to his election.

Article 38 does establish a religion--but not a particular denomination:

 XXXVIII. That all persons and religious societies who acknowledge that there is one God, and a future state of rewards and punishments, and that God is publicly to be worshipped, shall be freely tolerated. The Christian Protestant religion shall be deemed, and is hereby constituted and declared to be, the established religion of this State. That all denominations of Christian Protestants in this State, demeaning themselves peaceably and faithfully, shall enjoy equal religious and civil privileges.

 Obviously, the Court lost the original intent along the way.