Chapman’s Millrace, 438 South Mission Drive, San Gabriel, Los Angeles County, CA

STORED ON SITE. mchr
Significance: The millrace is an unreinforced masonry water conveyance feature with a U-shaped plan made with procured stone and cement mortar. The structure consists of two millrace "walls," which contained the water flow, and a raceway "floor" that directed water flow toward the mill. It powered Chapman's Mill, the key innovation of which was its mechanization through the addition of gears, transferring wheel from vertical to horizontal, adjustable speed and torque, and adjustable millstone spacing for different grains, making the mill one of the first examples of the Industrial Revolution in California.
Unprocessed Field note material exists for this structure: N1438
Survey number: HAER CA-2305
Building/structure dates: ca. 1821- 1823 Initial Construction