This first of two E-Lectures about distinctive features in phonology looks at the historical development of distinctive features from Trubetzkoy’s system of distinctive oppositions via Jakobson’s system of acoustic features to Chomsky’s and Halle’s system described in their influential work "The Sound Pattern of English." In a follow up E-Lecture today’s feature systems will be discussed and the primary motivations behind distinctive features in phonology will be exemplified.