Castle Rock is a 70-foot chalk pillar in the Smoky Hills of western Kansas, prominent above nearby badlands and widely recognized as one of the state’s best-known natural landmarks. Formed from chalk deposited when this region lay beneath an ancient inland sea, it was shaped over time by wind and water and named for its castle-like appearance. During the Overland Trail era, it served as a landmark on the Butterfield Overland Despatch route, helping guide travel across the open plains. Though fragile and increasingly damaged by weathering and climbing, it remains a notable symbol of the Kansas high plains despite the collapse of its tallest spire in 2001.