Kloochman Rock is a volcanic intrusion composed of pyroxene-rich andesite, formed when molten volcanic material was pushed into a fissure or crack, where it cooled and hardened. Andesite is a relatively hard fine grained material, and the pyroxenes appear as crystals within the rock. Over millions of years, the surrounding softer material eroded away, leaving the feature seen today. A local legend from the Confederated Tribes and Bands of the Yakima Nation tells of Chief Me-ow-wah, a well respected chief who did not want a wife. Nearby chiefs believed such a respected chief should marry, so they sent their most beautiful princesses to him. Me-ow-wah left his village to live alone in the mountains, but when his people found him and he realized they intended to make him return and take a wife, he consulted his father, a medicine man, and resolved to sacrifice himself and the potential brides. When the women arrived, he commanded them to stop, and they were all turned to stone, including Me-ow-wah. One of the women became Kloochman Rock, and Me-ow-wah became the nearby mountain now known as Goose Egg.