American Bison on Wildlife Loop Road in Custer State Park

American bison graze along Wildlife Loop Road, an 18-mile route through Custer State Park in the Black Hills of South Dakota. The park maintains a herd of roughly 1,300 bison, one of the largest publicly held herds in the world, descended from animals reintroduced in 1914 after the species neared extinction on the Great Plains. Each September, the park holds its annual Buffalo Roundup, drawing thousands of spectators to watch cowboys and volunteers drive the herd across the prairie for health checks and population management. Bison bulls can weigh up to 2,000 pounds, and their grazing patterns help sustain the mixed-grass prairie that defines much of the park's 71,000 acres.