Religious intolerance has existed throughout history, and it still thrives today in many parts of the world. The idea that individuals have a right to practice their religion freely is a relatively modern one. Religious tolerance was—and remains—one of the bedrock freedoms in the United States, but it has never been embraced in many parts of the world. In general, rulers have given more weight to political control than to religious toleration. For example, Constantine the Great's decision to grant religious freedom in the fourth century was unprecedented, and it cemented his grasp on power.
France had a long struggle over religious rights. The Huguenots, French Protestants, were persecuted for many years. In 1598, the Edict of Nantes gave the Huguenots some religious freedom, but future French kings often reneged and reverted to persecution of Protestants. Religious freedom was an important facet of the French Revolution in 1789.
The Spanish, conquerors of most of Latin America, used religion as a justification for the extermination of Native Americans. The Inquisition was strong in Spain, and Jews were expelled in 1492. Father Bartolomé de las Casas, who argued for humane treatment of Indian non-believers, was part of a small minority.
The United States's history with religious toleration is mixed. Many of the early colonies did not allow religious freedom. Pennsylvania, on the other hand, was founded on the principle of religious toleration. When the US was created, freedom of religion was enshrined in the First Amendment. But religious intolerance has flared intermittently. For instance, the Know-Nothing Party of the mid-nineteenth century was strongly anti-Catholic, and the US did not have a Catholic president until the mid-twentieth century.