7 votes

Purdon Crossing Bridge


Purdon Crossing

Historic American Engineering Record (Library of Congress)

BH Photo #164993



This is the only bridge of its kind still in use in the state of California and is HAER documented.


Pratt half through through truss bridge over South Yuba River on Purdon Road
Nevada County, California
Open to traffic
Built 1889, rehabilitated 2013
- Cotton Brothers of Oakland, California
Pratt half-height through truss with road deck carried half way between top and bottom chord.
Length of largest span: 145.0 ft.
Total length: 191.9 ft.
Deck width: 11.2 ft.
Vertical clearance above deck: 14.7 ft.
Posted to the National Register of Historic Places
Also called
Purdon Road Bridge
Approximate latitude, longitude
+39.32771, -121.04651   (decimal degrees)
39°19'40" N, 121°02'47" W   (degrees°minutes'seconds")
Approximate UTM coordinates
10/668379/4354963 (zone/easting/northing)
Quadrangle map:
Nevada City
1695 ft. above sea level
Average daily traffic (as of 2009)
Inventory numbers
CA 17C-24 (California bridge number)
BH 11226 (Bridgehunter.com ID)
Inspection report (as of August 2017)
Overall condition: Poor
Superstructure condition rating: Good (7 out of 9)
Substructure condition rating: Poor (4 out of 9)
Deck condition rating: Fair (5 out of 9)
Sufficiency rating: 12.9 (out of 100)
View more at BridgeReports.com

Update Log 

  • June 7, 2019: Updated by Erik Hoffman: Added category "Lally columns"
  • June 19, 2017: New Street View added by Dana and Kay Klein
  • October 21, 2015: Updated by Erik Hoffman: Added category "Last of its kind"
  • August 9, 2015: New Street View added by Erik Hoffman
  • May 21, 2013: Updated by Nathan Holth: Bridge to be rehabilitated.
  • November 12, 2010: Updated by Craig Philpott: added builder and photos
  • May 11, 2010: Updated by Craig Philpott: added photos
  • March 16, 2010: Updated by Craig Philpott: Updated design and added streetview



Purdon Crossing Bridge
Posted August 11, 2019, by Daniel

Just curious, what makes this last of it's kind? Pinned half through?

Purdon Crossing Bridge
Posted June 19, 2017, by Nathan Holth (webmaster [at] historicbridges [dot] org)

It is a relief to hear that one of the most significant and unique historic bridges in California remains after the floods!

Purdon Crossing Bridge
Posted June 19, 2017, by Robert Elder (robertelder1 [at] gmail [dot] com)

That is great news. Thanks for the update. We were concerned about this one.

Purdon Crossing Bridge
Posted June 19, 2017, by Anon

I drove across the bridge twice yesterday while running a bird survey route. Yes, it is still standing even after our very rainy winter.

Purdon Crossing Bridge
Posted January 9, 2017, by Erik Hoffman

Does anyone know if this bridge made it through the January 2017 flood?

Purdon Road Bridge
Posted November 12, 2010, by Craig Philpott (cphilpott [at] puc [dot] edu)

To quote from: "Historic Highway Bridges of California" 1990, California Dept. of Transportation: "The Purdon Bridge is the only known example in California of a half-through truss, an unusual truss form in which the deck is carried approximately half-height between the top and bottom chords... The bridge was designed and built by Cotton Bros. and Company.

Purdon Road Bridge
Posted November 12, 2010, by Anthony Dillon (spansaver [at] hotmail [dot] com)

Very unique! Have never heard of a "half" through truss

Purdon Road Bridge
Posted March 30, 2009, by Mistie (mattskitten [at] sbcglobal [dot] net)

The bridge is open and can be crossed by vehicle. It is a single lane bridge.