In the autumn of 1872, the United States economy ground to a sudden, terrifying halt. The cause was not a stock market crash or a human pandemic, but a highly contagious strain of equine influenza. Within weeks, millions of horses were paralyzed by sickness, silencing the bustling streets of major American cities. Before the combustion engine, horses were the vital gears of urban infrastructure. The Great Epizootic exposed the fragility of a society completely dependent on animal labor. Streetcars stopped, food rotted at docks, and fire engines could not be pulled—a vulnerability that directly fueled the catastrophic Great Boston Fire of 1872. Samuel Harris chronicles this forgotten logistical nightmare. He examines the hidden mechanics of 19th-century supply chains and how a single biological variable brought the Industrial Revolution to its knees. The book highlights the perilous consequences of building a monolithic transportation network with no fallback systems. History proves that single points of failure inevitably collapse. Read this fascinating account to understand the deep vulnerabilities in our own modern infrastructure and the true cost of unchecked dependencies.