This talk will present a brief overview of the advances in theory and experiment that led tothe discovery of the expanding universe: from Slipher’s early observations of the redshifts of the distant nebulae to the distance/redshift measurements of Hubble and Humason, from Einstein’s relativistic model of a static universe to the dynamic models of Friedmann, Lemaitre and others. The presentation will include a brief discussion of the relative importance of each contribution in the context of the history and philosophy of science.