As master distiller at Heaven Hill since 1975, Parker Beam is one of the most powerful and influential men in American whiskey. The respected master distiller has not only made Heaven Hill's whiskey, but over the past 39 years has shaped it in a way few distillers get the chance to do. In fact, when you compare Bourbons of 20 years ago to many of today's prized bottlings—which are older, drier and show much more wood influence than their predecessors—you realize that Beam's tastes have influenced more than just Heaven Hill's bottlings. It's been a time of change for Bourbon, and Parker Beam has had an outsized effect on it. Wine Spectator's Lew Bryson explains.