The roots of IOs can be traced back to the emergence of the modern international system after the Peace of Westphalian in 1648.

Because the early international system had been mainly dominated by European nation states, first IOs emerged in the 19th century in Europe.

The Congress of Vienna (1815) created a more convenient atmosphere for the development of IOs. 

The establishment of the United Nations (UN) has provided an international platform for states.

The League of Nations is the first permanent IO that was established for the maintenance of international peace and security.

It was only after the First World War that modern IOs started to emerge. Archer considers the Paris Peace Conference of 1919 as the starting point of contemporary IOs. After the Conference, the League of Nations and International Labour Organization (ILO) were established as the leading modern IOs.