Oxford University Press has published an interactive online tool charting the history of international law. It is available here.
The blurb from the website states:
We have created a concise timeline mapping the broad history of public international law with particular attention paid to the signing of major treaties, the foundation of fundamental institutions, the birth of major figures in international law and milestones in the development of some of the field’s best-known doctrines. There are varying opinions on where to start in the history of international law, as well as arguments around periodising the dynamic developments, though for this project we have started our timeline with the Treaty of Tordesillas in 1494. Explore some of the major developments in the history of international law and read more by clicking through to freed-up chapters from the Oxford Historical Treaties, the Max Planck Encyclopaedia of Public International Law, relevant book chapters, blog pieces and journal articles.