Steptoe Butte is a quartzite island jutting out of the silty loess of the Palouse hills in Whitman County, Washington. It is contained by Steptoe Butte State Park. The rock that forms the butte is over 400 million years old, in contrast with the 15–7 million year old Columbia River Basalts that underlie the rest of the Palouse. Steptoe Butte has become an archetype, as isolated protrusions of bedrock, such as summits of hills or mountains, in lava flows have come to be called steptoes.