The history of Ireland is the story of its past. Ireland is now divided into the Republic of Ireland, and Northern Ireland which is part of the United Kingdom. People began farming on Ireland thousands of years ago. The Celts moved there about 2,500 years ago. Ireland was divided into many small kingdoms. When Christians arrived, most Irish people became Christian. The Vikings and later the Normans invaded in the Middle Ages. Eventually, Ireland became part of the United Kingdom, with Great Britain. In the 1920s, most of Ireland became a separate country, but Northern Ireland stayed in the United Kingdom.