The history of human activity on Polish soil spans thousands of years. Throughout the late antiquity period it became extensively diverse, with various cultures and tribes settling on the vast Central European Plain. However, it was the Western Polans who dominated the region and gave Poland its name. The establishment of Polish statehood can be traced to 966, when the pagan ruler of a realm coextensive with the territory of present-day Poland embraced Christianity and converted to Catholicism. The Kingdom of Poland was founded in 1025 and in 1569 cemented its longstanding political association with Lithuania by signing the Union of Lublin. This union formed the Polish–Lithuanian Commonwealth, one of the largest (over  in area) and most populous nations of 16th and 17th century Europe, with a uniquely liberal political system which adopted Europe's first modern constitution, the Constitution of 3 May 1791.