Civil War Era Bridge Types at Black Bridge Location
Today, Black Bridge carries trains over the Codorus Creek as railroad traffic moves between York and Emigsville. This bridge is a prominent feature viewable from the new section of the rail trail, recently opened in Springettsbury Township.
The August 11th, 1863, issue of The Adams Sentinel tells about the Northern Central Railway plans to build permanent replacement bridges to replace temporary bridges that were erected within days after being destroyed during the Civil War. The Northern Central Railway bridges were destroyed during June 28 and June 29 of 1863 when Confederate Troops invaded York County. (see Rebels destroy the Codorus Bridge (Black Bridge)).
The Adams Sentinel article states that the new permanent bridges “over the Codorus near Loucks’s mill, the Gut and the Conowago, are to be of wood of the Howe-truss patent.” The Eighth Annual Report of the Northern Central Railway, i.e. as of December 31, 1861, records that the Codorus Bridge (# 98), Gut Bridge (#118) and Conewago Bridge (# 119) were all initially built as 2-span Howe Type bridges in 1848. These were the three longest span bridges on the Northern Central Railway in York County; of which Codorus Bridge (now Black Bridge) was the longest, at 336-feet total length.
In 1848, the York and Cumberland Railroad (later part of the Northern Central Railway) was in the process of being built from York to Harrisburg, therefore the bridges destroyed by the Confederates in 1863 were the original bridges. This railroad partly opened to York Haven by 1850 and rail connections to Harrisburg were completed in 1851.
In 1848, the Howe Truss bridge was a relatively new truss design; it was patented in 1840. Early on, it was a bridge type that thrived because of its heavy use of timber and minimal use of iron. The Howe Truss quickly became the preferred long span railroad bridge, not only because of its strength, but also railroads of that era favored this bridge for its ease to partially prefabricate offsite and to ship by rail.
A competing Pratt Truss bridge design was patented in 1844. This truss design was pretty much opposite the 1840 Howe Truss; the Howe having timber diagonals (in compression) slanting to the center of the bridge and vertical iron ties (in tension). The Pratt Truss has internal diagonals (in tension) slanting away from the center of the bridge and verticals in compression.
Both the Howe Truss and Pratt Truss bridge types transitioned from a combination of wood and iron construction to all iron construction; although the design of the Pratt Truss lent itself to a smother transition. The further transition to all steel bridge construction heavily favored the Pratt Truss type, which is the reason photos of Howe Truss bridges (of any construction) are rare.
The bridge that the Confederates encountered and destroyed in 1863 at the Black Bridge location has been described a whole host of ways. Some histories say it was a metal girder deck bridge, some say it was an iron truss bridge, however very few note it being of primarily wood construction; which the findings of this post point to as the actual bridge type.
The records of the Northern Central Railway indicate the original bridge is of a Howe Truss type. The Adams Sentinel article notes the new permanent bridges will be “of wood of the Howe-truss patent.” If the original bridge were all-iron, why would the railway suddenly take a step back to an older material; i.e. wood. Furthermore in the bridge design books that I’ve read, I’ve never seen any all-iron Howe Truss bridges built before the mid-1850s, therefore the original 1848 bridges being of primarily wood construction appears logical.
The basic design of a primarily wooden Howe Truss Bridge is shown in this diagram. The design features timber diagonals (in compression) slanting to the center of the bridge and vertical iron ties (in tension).
The following photo shows a typical 2-span Howe Truss Bridge of the construction common in the mid-1800s. This photo is of a Howe Truss Railroad Bridge that was in Boone, Iowa, and is from the Iowa State Archives. The Codorus Bridge (now Black Bridge), built in 1848, probably appeared similar.
I discovered that primarily wooden Howe Truss Bridges were easily destroyed during war. General Herman Haupt was known for this civil engineering and rapid bridge rebuilding skills, however he also devised methods to efficiently destroy bridges in the south. One such method focused on destroying the primarily wooden Howe Truss bridge by boring only two strategically placed holes and inserting explosive charges, named the “Haupt’s Torpedo.” The Library of Congress collections contain the following photo of a primarily wooden Howe Truss bridge in Northern Virginia, showing a man boring a hole in the bridge timber and a man sitting, holding a “Haupt’s Torpedo.”
Related posts include:
- On the Job at Black Bridge
- Blackbridge Road went under Black Bridge
- How Black Bridge got its Name
- Pinpointing when Black Bridge got its Name
- Covered Railroad Bridge over the Codorus Creek
- 4-Lane Interstate planned through Downtown York?
- Guess the Time Required to Paint an INCREDIBLY Long Bridge
- North Penn Street ‘Drawbridge’ was raised with Muscle Power
- Eagle Nest within 700-feet of Route 30