California Historic Bridges and Tunnels in Digital Form

Purdon Road Bridge over the South Yuba River in Nevada City, California. One of two half-through truss bridges left in the state. Photo courtesy of the HABS/HAER Collection

Forum Question: If you wanted to showcase historic bridges in your area online, how would you do that? Would you focus on existing bridges or include those that were unique but no longer exists? How much information and photos would you add about the bridges?

The first time a website appeared which showcased many existing historic bridges in a region was the one produced by the Minnesota Historical Society.  Created in 1996, the historic bridge page featured as many as 100 bridge examples from all over the state. Even though the website has changed hands and is now part of the Minnesota Department of Transportation, many of the bridges noted are still in service today in one way of another.

California has just recently launched its website, showcasing its list of historic bridges in the most populous state in the Union. By clicking here on CalTrans Digital Collection website, you will have a chance to read more than 20 pages worth of hundreds of historic bridges and tunnels that still exist in California.

Interesting enough, the website features photos and documentation conducted by CalTrans, the State Historical Society, local historical groups and even HABS-HAER, containing information on the bridge type, location of the bridge, and the history of its construction as well as its association with the area it is located. Most of the photos were taken between 1975 and 2004 with the majority of the bridges being determined eligible for the National Register of Historic Places as of 2004. Some of the bridges have been replaced yet many others have been rehabilitated and retrofitted to withstand earthquakes, which are common in the Golden State.

This includes this bridge, the Purdon Road Bridge, spanning the South Yuba River near Nevada City. Built in 1895 by Cotton Brothers and Company, one of many California bridge builders that existed during that time, the Purdon Bridge was one of only two half-through truss bridges in the state, meaning the roadway is built halfway between the bottom and top portions of the truss. The bridge was scheduled to be rehabilitated in 2013, but it is unknown whether that has already taken place. More information on the bridge can be found here.

The digital collections are well detailed and has information on historic bridges that are considered significant on the state and national scale, yet some of them have since been replaced for structural reasons. There are also other bridges not listed in the collections but deserve some attention, including the wooden truss bridges in the northeastern part of the state.  But given the website’s infancy, it is more likely that the collection will become bigger in the future.

This leads to a pair of questions for the readers:

1. Apart from the bridges listed in the collections, including the Golden Gate, Vallejo and Bay Bridges, what other bridges should be listed? This includes bridges scheduled to be replaced in the next 10 years, like some in Los Angeles.

2. The Buellton (US 101) Bridge features seven through truss bridges that were relocated to Iowa and elsewhere in the 1950s. This bridge represents an example of historic bridges that have long since been nonexistent. Should these bridges be added to the list and if so, which ones?

This guide should provide other state agencies and organizations to compile a database of their own. Already some on the private scale, like and in the US and in Europe exist. But there are only a quarter of the states in the US that have such a database. It is time for others to join the bandwagon, but the question is how. Perhaps suggestions based on the questions presented at the beginning of the article will help, yet the best suggestion is to ask the experts who have constructed it to see how the database should be built and how the information should be reader-friendly.




Mystery Bridge 11: Wooden truss bridge in California

All photos (unless noted otherwise) courtesy of Aimee Stubbs of Lassen County, CA; used with permission

There is sometimes a misconception as to determining the meaning of a wooden covered bridge. Many people have a tendency of considering bridges, like the one above to be a covered bridge. Yet the definition of a covered bridge is different. A covered bridge is a truss bridge that is covered by siding and most of the time, a gabled roof. There are many examples of covered bridges that exist in the US and Europe, including the Marysville Covered Bridge, located at a park near Knoxville, Iowa.

Photo taken by the author in August 2011

But going back to this mystery bridge, the bridge made of wood is considered plainly a wooden truss bridge, whose wooden beams are connected with nuts and bolts but are neither pin-connected, welded nor riveted. There were numerous wooden truss bridges that were built during the second half of the 1800s and fewer that were built between 1900 and 1960. There are only a handful of these bridges that exist in the US for wood has the shortest lifespan of any bridges made of other materials, and is one with the highest maintenance- it needs to be varnished and painted regularly to ensure that they last just as long as bridges made of iron and/or steel.

The mystery bridge featured here is located in eastern California, spanning the Middle Yuba River between the Milton Reservoir and dam and the Jackson Reservoir, just 500 feet west of Heness Pass Road. The bridge features three spans of a double-intersecting Warren pony truss (shaped in a Howe lattice design) made of wood. Judging by its appearance in the pictures presented below, the wooden truss bridge features both riveted connections (on the top chords) and bolted connections, where intersecting beams are connected with bolts and nuts that were drilled into the wood.  The bridge was discovered by Aimee Stubbs while on a camping/ motorcycle trip in 2011 only to revisit the bridge again this past summer.

The bridge appears to have seen better days as it partially collapsed some time ago (although it not pinpointed as to when it happened), and only one of the truss spans is still standing. Since it served a dirt road located not far from the county road, the bridge and road seemed to have been abandoned, with nature taking its course on both. To reach the bridge via dirt road would require walking to the structure, which is challenging given the landscape where the bridge is located.  According to Stubbs, the Middle Yuba River is infamous for its recurring floods, causing damage and erosion to the bridge and the road. Yet there is no information on the bridge’s history that was found with the exception of the fact that the river separates both Sierra and Nevada Counties, two counties that were created in 1851-2 after seceding from Yuba County.

Ms. Stubbs has been researching this bridge since finding it for the first time and needs your help. With three spans, this bridge is one of the rarest in the country, if not the world. Yet its recent demise due to its collapse makes it even more important to find information on the structure so that people are aware of its existence (or at least its partial existence). If you have any information pertaining to the bridge, please contact her using the following information below.  The Bridgehunter’s Chronicles will keep you posted as soon as information comes to light on this unique structure. If you know of another bridge that is similar to the one shown here and still exists today, please contact Jason D. Smith using the contact details below as well. That information will be added as well.

The Bridgehunter connects the past with the future through research and preservation of historic bridges in the present.

Contact details:

Aimee Stubbs:

Jason D. Smith (The Bridgehunter’s Chronicles):























Photo of the collapsed portions of the bridge