Originally determined eligible in the Caltrans 1985 Historic Masonry Bridges in California Thematic Resources study; its continued eligibility was confirmed in the 2003 Caltrans Historic Bridge Inventory update: Masonry Bridges. In 2005, it was individually listed on the National Register under the Historic Highway Bridges of California MPS.
Garnett Creek Bridge is a three-span, earth-filled closed-spandrel masonry-arch bridge. The masonry structure is composed of square-cut stone laid in irregular courses. Both railings are comprised of square-cut stone.