Sulphur Mountain, Yellowstone

Thomas Moran's sketch captures the dramatic geology of Yellowstone's thermal features. Working in pen, Moran rendered the mountain's jagged ridges and layered formations with quick, economical lines—a field study rather than finished composition. Moran (1837–1926) spent decades documenting the American West, from the Grand Canyon to Yellowstone, translating raw landscape into both watercolors and engravings for mass publication. His sketches served as working notes for larger works, preserving immediate observation before translation into gallery paintings. This rapid notation reveals his method: establish topography through confident contour, suggest depth through overlapping planes, record geological character through linear accent.