Jim Brandenburg / American Bison (Bison bison) herd on prairie with quartz, Blue Mounds State Park, Minnesota

Jim Brandenburg / American Bison (Bison bison) male, Blue Mounds State Park, Minnesota

Jim Brandenburg / American Bison (Bison bison) herd on prairie, Blue Mounds State Park, Minnesota

Jim Brandenburg / Trees at night, Blue Mounds State Park, Minnesota

Jim Brandenburg / American Bison (Bison bison) herd in grassland, Blue Mounds State Park, Minnesota

Jim Brandenburg / Tree in tallgrass prairie, Blue Mounds State Park, Minnesota

Jim Brandenburg / Sioux Quartzite in tallgrass prairie with oncoming storm, Blue Mounds State Park, Minnesota

Jim Brandenburg / Common Hackberry (Celtis occidentalis) tree at sunset, Blue Mounds State Park, Minnesota

Jim Brandenburg / Sioux Quartzite on tallgrass prairie, Blue Mounds State Park, Minnesota

Jim Brandenburg / Sioux Quartzite, Blue Mounds State Park, Minnesota

Jim Brandenburg / Common Hackberry (Celtis occidentalis) and Sioux Quartzite, Blue Mounds State Park, Minnesota

Jim Brandenburg / American Bison (Bison bison) herd in winter, Blue Mounds State Park, Minnesota