top of page


Population Percentage Christian Map
Crucifixion by Agnolo Gaddi, between 1390 and 1396

Crucifixion by Agnolo Gaddi, between 1390 and 1396

Christianity is the world's biggest religion, with about 2.2 billion followers worldwide. This monotheistic religion is based on the teachings of Jesus of Nazareth who later became known as Jesus Christ because his believers think he is the Son of God.  Jesus was crucified around 33 CE in Jerusalem—a very important city to Christians.  Old Jewish writings said a leader would die and rise from the dead to lead the people.  Christians believe that Jesus rose from the dead and appeared to his disciples (followers), which made him the Messiah (Savior) promised in the Old Testament.  Most people who lived in the time of Jesus did not believe he rose from the grave.  Today, Jews are awaiting the coming of a Messiah or Savior, while Christians believe that Jesus Christ was the Savior.  Christians belief in God is complicated.  They believe in God, Jesus, and a spirit form of God called the Holy Spirit.  Christian's belief in God is what is called the Holy Trinity—the Father, the Son, and the Holy Spirit--they believe these are 3 forms of the same "God", similar to how water can exist in 3 forms of liquid, gas (water vapor), or solid (ice). 

Christianity originally developed as a part of Judaism.  Jesus was a Jew who was born in 1 CE in Bethlehem.  Most of his life is a mystery, as there are no records of his life except his birth, a brief time in his yearly childhood, and 1-3 years of adulthood when he preached and was crucified.  Christianity didn’t just happen immediately.  For nearly 100 years Christianity was not a separate religion, but a denomination (subgroup or branch of a larger organization) of Judaism.  Many people who followed more traditional Jewish beliefs viewed Jewish Christians negatively. Initially, the main followers of Christianity were just the family of Jesus and the few apostles that were still alive.  Jesus preached new ideas that many Jews and Romans viewed as rebellious--it was dangerous to be a follower of Jesus in the early years.  The number of followers greatly increased when some local leader around Jerusalem to Christianity. Later, many Romans began to convert to Christianity which dramatically increased the number of Christians worldwide. 

Early Christian Geography Map
The Christian Martyrs' Last Prayer painting

The Christian Martyrs' Last Prayer by Jean-Léon Gérôme (1863–1883, Walters Art Museum)

Jesus lived for 33 years before being crucified by the Romans.  Early Christians were not popular with Jews or Romans.  Many of Jesus's apostles were executed such as Peter who was crucified upside down in 64 CE. James the Just, Jesus's brother was crucified, then stoned, and finally beaten to death by wooden clubs.  Persecuted means they were treated badly or harassed.  However, by the year 391 CE Christianity became the most popular religion in Rome.   The Roman Empire spread Christianity to Europe. Christianity slowly became popular with the people in Europe. During the next 100 years Rome lost control of its empire. Europe developed the most powerful kingdoms and became independent of Rome by the year 476 CE.  Christianity became the dominate religion over the next 500 years. During this same time, a new religion was developing in the same area where Christianity developed. This new religion was called Islam.

Islam became the dominate religion in the Middle East, including the area around Jerusalem. Starting around 1100 CE the kingdoms in Germany, England, France, and Spain wanted to take control of the areas around Jerusalem. They thought of this place as their Holy Land, but so did the Muslims (believers of Islam). For the next 200-300 years, kingdoms launched several invasions of the Holy Land called the Crusades--they were mostly unsuccessful. Despite this, these kingdoms power was growing. Science and new technologies allowed them to sail the rough ocean waters farther than ever before. European kingdoms explored the world and developed outposts or colonies around the world. They spread the Christian religion to the native people living near their colonies in America, Africa, Australia, and South America. Sometimes they spread their version of Christianity by force. 

Battle of Inab painting

Nūr-ad-Din's victory at the Battle of Inab, 1149. Illustration from the Passages d'outremer, c. 1490

Martin Luther painting
Image of Martin Luther's Ninety-five Theses

Martin Luther and his Ninety-five Theses he nailed to a church door in 1517

During the 1500's, Martin Luther challenged some of the beliefs and practices of Christians. The main disagreement came from the authority and power of the pope. He and his followers split from traditional Christians. Traditional Christians became known as Catholics or Roman Catholics and Martin Luther's followers became known as Protestants.  This is known as the Protestant Reformation. This split causes a great deal of fighting and war for many years to come and its effects can still be felt today. 

The Christian place of worship is called a church. They are often built in the shape of a cross with the altar facing east towards the rising sun.  Christian spiritual leaders are called priests or ministers.  Christians believe priests have a special relationship with God.  The Bible is the Christian holy book.  It is divided into the Old Testament (Jewish book) written before Jesus and New Testaments.  Most versions of the New Testament have 27 "books" or parts.  They were written in Greek, some were written over 100 years after the time of Jesus.  The first parts of the New Testament were written about 20 years after Jesus was crucified, about 51 CE to 80 CE, however, Christians believe the writing was inspired by God.  Some parts were written hundreds of years after Jesus lived. The New Testament was finally put together mostly as it is today in the mid-300's CE.  There are many stories or "gospels" not included in the official Christian Bible. 

The Christian bible
Pie graph showing major Christian denominations

There are different branches or denominations of Christianity because some Christians worship in different ways and believe in different parts of the Bible.   There are 3 main denominations in Christianity--Roman Catholic, Eastern Orthodox, and Protestant.  Each denomination is further divided into its own branches.  Methodists, Mormons, Baptists, and Quakers are just a few of the dozens (maybe hundreds) of Christian denominations.  They all worship in slightly different ways, different times of the day, saying different prayers, or believing slightly different things, but most believe in certain core ideas such as heaven, and the resurrection of Jesus.  Differences center around the role of the pope, how churches are organized, understanding of the Holy Trinity, historic traditions, and many small practices and customs. 


The most important Christian holiday for all Christians is Easter, which celebrates the resurrection of Jesus.  Christmas is the celebration of the birth of Jesus. However, these holidays are are also celebrated by people who do not follow the religion. The Christian holy day is Sunday. 

bottom of page