Running is one of the simplest human movements, yet in the United States it grew into one of the most powerful everyday sports. The Runner’s Republic: How Running Became America’s Everyday Sport tells the fact-based story of how running moved from Indigenous foot travel, colonial contests, pedestrian spectacles, college tracks, Olympic stadiums, and city marathons into neighbourhood streets, public parks, school courses, treadmills, trails, and charity race calendars across America. From the Boston Marathon and the rise of road racing to Title IX, women’s distance running, the jogging boom, the running shoe marketplace, grassroots clubs, adaptive athletes, charity miles, GPS watches, ultramarathons, and public-health campaigns, this book follows the people, institutions, races, and cultural shifts that made running part of ordinary American life. It explores elite champions and everyday runners alike, showing how the same sport could belong to Olympic medalists, school athletes, first-time 5K finishers, marathon dreamers, wheelchair racers, trail ultrarunners, and those simply running for health, memory, or community. Written in a polished, narrative, fact-only style, this book presents running not as a single race or era, but as a national habit shaped by endurance, access, technology, inclusion, commerce, crisis, and personal meaning. It is a story of roads, tracks, trails, clubs, cities, volunteers, finish lines, and the millions of ordinary steps that turned running into one of America’s most enduring sporting cultures.