Looking at the island of Palm Beach today, one is hard pressed to visualize the dense tangle of Palmetto brush and mangroves that railroad tycoon Henry Flagler found there in April 1893. Over the next 125 years, Palm Beach has become synonymous with exclusivity—especially its most famous residence, "Mar-a-Lago." Looking back on this transformation, the author of Battle for the Big Top tells a story of ascendance, architectural one-upmanship, and decadence that includes sewing machine heir Paris Singer, Marjorie Merriweather Post, and Donald Trump.