Christianity started with the birth of Jesus Christ in Bethlehem; however, it technically spread from Jerusalem where Jesus lived most of his life.

The roots of Christianity began with the birth of Jesus Christ. His birthday is celebrated on December 25, every year by Christians around the world. He was born in Bethlehem; however, he lived most of his life in Jerusalem.
Jesus was crucified for his practices; however, after three days in the tomb, it is believed that he rose from the dead and greeted his family, friends, and followers. Those who believed in him were known as Christians. These events occured around the beginning of the first century, A.D.
It is believed that forty-nine days after Jesus' Resurrection, Peter preached the first public sermon, and the Holy Spirit came to the apostles. This day was known as Pentecost. Three thousand baptisms were celebrated early on in the history of Christianity, and the religion began to spread rapidly. After Jerusalem, Christianity spread to Judea, Samaria, and Galilee. Within the first few centuries of the A.D. period, Christianity spread far into the Roman Empire.
Even though the answer to where did Christianity originate is Jerusalem, Christianity has spread all over the world. The religion continues to grow, and followers continue to engage in the traditional practices of Christianity. Various sects have formed that have differering beliefs, but they all center around a few shared fundamental principles.