Chasing the highest energy cosmic rays: From 1948 to the present

After a brief review of the discovery of extensive air showers, I summarise the remarkable advances made in the decade 1948–1958. During this period many of the techniques of instrumentation and analysis that are used today were introduced. I then discuss current data with emphasis on recent work on the measurement of the mass composition between 1015 and 1017 eV and above 1018 eV, and on the energy spectrum at the highest energies.