Hogg Rock is a small volcanic mountain near Santiam Pass in Oregon’s northern Cascades, rising to 4,823 feet between Three Fingered Jack and Hayrick Butte. Its shape and geology identify it as both a tuya and a lava dome, formed when andesite erupted beneath ice during the Pleistocene about 80,000 years ago and later was modified by glacial erosion. Unusual in the Cascades for its andesite dome, it also has a notable human history. Named for Col. T. Egenton Hogg, it became linked to his failed Oregon Pacific Railroad scheme in the late 19th century, and nearby remains also reflect the area’s later role in travel and winter recreation.