The concept of religious freedom under the United States Constitution.

During the time of birth of the United States, no country on the continent of Europe were church and state separated. People who were not accepting or practicing the religion of the state were often persecuted and killed! For example, Catholic France persecuted Huguenots who were known as French Protestants in the 1700s.

In some countries, people practicing a religion other then the state religion were "tolerated" despite not being legally permitted to vote and hold political office. The United States became the first country where church and state were completely separated in 1785. In 1787, the country's leaders wrote up the Bill of Rights guaranteeing religious freedom for all. All states followed suit in 1789. Establishment of religion is unconstitutional as the founding fathers believed. Presidents James Madison and Thomas Jefferson fought hard for religious freedom. William Penn believed no state has the right to interfere with religion of its inhabitants.

But not all these religious freedom ideologies were shared by all the colonists. Virginia had set up their state religion with the Church of England. Maryland was under Catholic rule. Some states had their own state religion and didn't permit Jewish people to live in their state. Maryland outlawed Jewish people from living in the state until 1827 when the US Supreme Court ruled out banning people that believed in certain religions from living in any states was unconstitutional. By 1960 religious freedom was allowed in all states in the US.

The United States Constitution guarantees religious freedom for ALL citizens within the wonderful country of the United States. The United States Constitution guarantees that church and state be separated. The US Government has no right to interfere with religion of its inhabitants or their religious beliefs. Which is why we in 2015 have freedom of religion.
That's the concept of religious freedom under the United States Constitution.