The “Men of Progress” painting, from 1862, shows the first Secretary of the Smithsonian surrounded by a group of scientists and inventors credited with “altering the course of contemporary civilization.” But what may be most remarkable about this tableau is who’s not there. To mark the 175th anniversary of the Smithsonian’s founding, the National Portrait Gallery’s Portraits podcast takes us back in time – to trace how the concept of progress has evolved, and who current Smithsonian Secretary Lonnie G. Bunch III would put in his “portrait of progress.”