From climate models to Google Earth to the Anthropocene concept, global knowledge underpins much of how we understand our world. Yet, global views are not intuitive or ‘natural’: they have to be constructed through complex processes of coordinated measurements involving diverse actors operating in a range of contexts. In this talk, Lehman explores the oceanographic program of the International Geophysical Year (IGY, 1957-58) to argue that there are distinctive stakes to science that aims to be global from the start. In particular, Lehman will show how the global relations of the IGY oceanographic program knitted together old and new forms of American imperialism to produce contemporary understandings of the world ocean.