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 bridgehunter.com and historicbridges.org in the US and Structurae.net 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.