In mid-July, NASA's New Horizons spacecraft flew past Pluto after a 9-1/2-year journey. But really this historic encounter has been 85 years in the making, ever since 24-year-old Clyde Tombaugh discovered this enigmatic body at the edge of our planetary system. Today we realize that Pluto is among the largest objects in the Kuiper Belt, even though initially it was believed to be a body perhaps as massive as Earth. This presentation traces the history of Pluto – from predictions of its existence, to the discovery of its moons, to its "demotion" to dwarf-planet status – and explores the amazing, unexpected findings revealed by New Horizons. An award-winning writer and communicator, Kelly Beatty specializes in planetary science and space exploration as Senior Editor for Sky & Telescope magazine.