Rimrocks, Sandstone cliffs in Billings, United States.

The Rimrocks are rimrock sandstone formations of Eagle Sandstone that outcrop in sections of Billings, Montana. The rock is pale beige and tan, with a flat, grassy top and a steep, eroded face cut by vertical fissures and weathered bands; a lower, blocky ledge of the same sandstone steps down on the left. The tallest single section begins at the eastern border of downtown at Sacrifice Cliff and runs south for roughly 18 miles through Coburn Hill.

These cliffs formed roughly 80 million years ago when the area was the shoreline of an ancient inland sea. Over millions of years, the Yellowstone River carved and shaped the rock layers into the steep walls visible today.

The name Sacrifice Cliff, at the eastern edge of downtown Billings, is attached to the tallest single section of the Rims, which runs south for roughly 18 miles through Coburn Hill. In the late 1960s resident Brooke Wirkkala and the group Better Billings gathered signatures to keep the Rims in their natural state; when that failed, the Billings Gazette proposed a national monument, which the National Park Service turned down as being of less than national significance.

Several parks and trails along the formation provide different access points for visitors of varying fitness levels. Wear sturdy footwear and plan your visit during spring or fall when temperatures are more comfortable for walking.

Early European traders used natural crevices within the sandstone for shelter during harsh winters in the 1800s. Researchers later discovered remnants of these temporary dwellings hidden within the rock formations.