California Powder Works Bridge, Covered bridge in Paradise Park, Santa Cruz County, US.

The California Powder Works Bridge is a single-span covered bridge carrying Keystone Way over the San Lorenzo River. Its 163-foot Smith truss is built of Douglas fir, clad in vertical board-and-batten siding, and topped with corrugated metal; the roadway is 19 feet 3 inches wide.

The bridge was built in 1872 by the Pacific Bridge Company for the California Powder Works, whose main plant stood on the east bank of the San Lorenzo River from 1863 to 1914. After the works closed, a Masonic organization from Fresno bought the land and turned it into the Paradise Park summer colony. A 2015 National Historic Landmark designation recognized it as the best-preserved national example of the Smith truss.

The bridge carries Keystone Way, the private road of the Paradise Park Masonic Club, a summer colony the Masonic organization from Fresno laid out after buying the former powder works land. The truss type was marketed nationwide by the Smith Bridge Company and briefly competed with iron bridges. A posted 5-ton limit applies to traffic crossing it.

The bridge is accessible from the surrounding park roads and is available to walk across on foot to see the construction and design details. Visitors should be aware of posted weight restrictions and stay on designated walkways when exploring this historic structure.

The bridge is one of 23 known pre-1955 Smith truss bridges left in the United States, and a National Park Service survey found it the longest and among the best preserved. Its trusses are Douglas fir, its roof corrugated metal, and its sides vertical board-and-batten siding.