Built in 1886 at the corner of King Street and St. George Street in St. Augustine, Florida, the Lyon Building is one of the oldest surviving poured-concrete commercial structures in the American South. When the rest of the city was built of wood, Walter Lyon's heirs chose a new concrete method and built something meant to last. This is the story of a building that survived two fires, the Gilded Age, the civil rights movement, and 140 years of continuous use at the center of the oldest European-settled city in the United States. Drawing on primary sources, newspaper accounts, and architectural records, it traces the building through six distinct eras and the figures who shaped it.