1889 IC Bridge over Ohio River at Cairo, IL

(Bridge Hunter, this was in the same location as today's bridge)

The spans of this bridge were replaced in 1952.

"Consisting of a series of pinned Whipple through trusses, supported by stone piers, it was the longest metallic bridge in the world when completed, and its 518-foot channel spans represented the ultimate extension of the Whipple truss." [MissouriHistoricInventory]

Alexander Self posted
Illinois Central Bridge 1913
[Judging from the piers, the river is running high.]

We can see on the left side of the above photo that the approache spans were deck trusses.

Darrel Cornelius Summers posted
Antique black and white photograph of American landmarks: Bridge over the Ohio River at Cairo, Illinois.
Bj Sullivan: Likely before 1903 era...the Subway levees and First Concrete Levee has not been built.
Kristopher Isaac Barrington shared

Illinois Central Railroad Scrapbook posted

On March 29, 1886, the Kentucky legislature passed a bill giving the Chicago St. Louis & New Orleans Railroad the right to build a bridge across the Ohio River. The CStL&NO, as you may know, was an IC subsidiary. It was also the legal owner of most IC trackage south of the Ohio River. Generally speaking, whenever the IC embarked on a major construction project on trackage south of the Ohio River, the contracts were signed in the name of the CStL&NO, not the IC.

Politics played a heavy role in the bridge construction. Businessmen, politicians, and residents of Paducah lobbied heavily to have the bridge built in their city, instead of at Cairo. Thus, when the Kentucky legislature passed the bridge bill, the IC was given permission to build the bridge at three locations: within the city limits of Paducah, three miles upstream or downstream of the Paducah city limits, or at Cairo. Well, the IC did not yet serve Paducah, but they did have a major presence in Cairo, so naturally the bridge was built at Cairo.

Construction of the bridge "officially" began on July 1, 1887, however, works crews had actually been at work since mid-March. The first train crossed the bridge on October 29, 1889, and the bridge has been in continuous service since then. Several major changes have been made over the years. In 1905-06 the entire wooden approach trestle and all but a short section of the steel approach trestle on the Illinois side was filled in. Then in 1914-15 the bridge was strengthened to accommodate the new 2-8-2's. In 1934-45 the entire steel approach trestle on the Kentucky side was replaced along with the short section that still remained on the Illinois side.

But the most significant improvement took place between 1950 and 1952 when the spans across the river were replaced. New spans were constructed on a floating platform next to the spans they would replaced (the floating platform was actually two 200' deck girder spans used to replace a 400' span on the Kentucky side).+

Illinois Central Railroad Scrapbook posted
On March 29, 1886, the Kentucky legislature passed a bill giving the Chicago St. Louis & New Orleans Railroad the right to build a bridge across the Ohio River. The CStL&NO, as you may know, was an IC subsidiary. It was also the legal owner of most IC trackage south of the Ohio River. Generally speaking, whenever the IC embarked on a major construction project on trackage south of the Ohio River, the contracts were signed in the name of the CStL&NO, not the IC.
Politics played a heavy role in the bridge construction. Businessmen, politicians, and residents of Paducah lobbied heavily to have the bridge built in their city, instead of at Cairo. Thus, when the Kentucky legislature passed the bridge bill, the IC was given permission to build the bridge at three locations: within the city limits of Paducah, three miles upstream or downstream of the Paducah city limits, or at Cairo. Well, the IC did not yet serve Paducah, but they did have a major presence in Cairo, so naturally the bridge was built at Cairo.
Construction of the bridge "officially" began on July 1, 1887, however, works crews had actually been at work since mid-March. The first train crossed the bridge on October 29, 1889, and the bridge has been in continuous service since then. Several major changes have been made over the years. In 1905-06 the entire wooden approach trestle and all but a short section of the steel approach trestle on the Illinois side was filled in. Then in 1914-15 the bridge was strengthened to accommodate the new 2-8-2's. In 1934-45 the entire steel approach trestle on the Kentucky side was replaced along with the short section that still remained on the Illinois side.
But the most significant improvement took place between 1950 and 1952 when the spans across the river were replaced. New spans were constructed on a floating platform next to the spans they would replaced (the floating platform was actually two 200' deck girder spans used to replace a 400' span on the Kentucky side).
Erik Coleman Ironically (for Paducah) the P&I bridge near Paducah ended up saving the IC's traffic capacity in the early 20s.
Illinois Central Railroad Scrapbook Absolutely correct. IC had drafted plans to rebuild the Cairo bridge as a double track structure and the plans had even been approved by the War Department (which at the time was in charge of approving designs for bridges over navigable waters). But after crunching and recrunching the numbers, building the Edgewood Cutoff was determined to be cheaper and be more beneficial to the company.

Frank Smitty Schmidt posted
IC Cairo Bridge circa 1900.
Richard Koenig That's a pretty amazing photograph: large format, evocative, moody (not to mention historically informative beyond railroads with steam ship and logs in water).

Illinois Central Railroad Scrapbook posted

A northbound IC freight with 2-8-2 1538 in the lead rolls off the Ohio River bridge at Cairo, IL, on June 20, 1950. Within a few weeks crews will be replacing the spans of the bridge's superstructure. New spans were constructed on barges anchored next to the bridge. Once each new span was finished, the old span was rolled out of the way and then the new span was rolled into place. The old piers were repaired and reused.

This method of reconstructing the old bridge was chosen because it was cheaper, faster, and involved far less government red tape than building a new bridge.

The first new span was moved into position on October 16, 1950, and the last new spans were rolled into place on February 11, 1952.

Harvey Henkilmann posted
Illinois Central's massive Ohio River bridge at Cairo, IL c.1892
Mark Kta SmithMark and 343 others joined RAILROAD BRIDGES, TRESTLES, TUNNELS AND CUTS within the last two weeks. Give them a warm welcome into your community! IT STILL AMAZES ME THAT WE HAD THE TECHNOLOGY TO BUILD THESE STRUCTURES AT THAT TIME.
Daniel Herkes The engineering capability quickly outpaced the availability of materials needed to build structures that made use of them. This bridge is a case in point. It was too low and too lightly built to withstand the rigors of WWI's traffic demands. Yet better steel and designs were available. The IC simply drew from its experience and built a bridge. They could have built what they ended up with by 1935. Read this: http://bridgestunnels.com/.../cairo-bridge-illinois.../
[This is an interesting article. It talks about the foundations that were built to hold the piers in an area that has over 200' of sand and gravel. Also, the original plans were to build 150' upstream.. But when the river boat interests called for an 800' navigation span, IC decided to improve their existing piers and require the contractors to devise a span replacement technique that significantly reduced the outage. To put 800' in perspective, when the river boat interests required a 700' span for the Metropolis Bridge, they thought that would kill that project. Instead, the bridge builders called their bluff and built "the longest pin-connected simple through truss span in the world." So by being greedy and asking for 800'. they ended up with the old 518' spans.] 
Phil De Franco Not impossible (since it was built) and not so amazing. The principles of bridge building with metal structural members was well understood by the mid-1800's. Replacement of cast iron members with steel members was very common by the 1880's.
Paul Pierson Try to do it today and spend years on the paperwork.
Daniel Herkes True. Yet engineering disasters are all too real. Not just collapses, but other types. For example, the Cairo, IL bridge was a disaster for the city of Cairo. The IC trains no longer made use of the car ferry upon which the fortunes of the city were built. Cairo's decline dates from this time. Another disaster was an environmental one. Cairo was heavily defended from the Ohio and Mississippi rivers floods after the huge 1927 disaster. The city, although in decline, was heavily leveed on both sides of the rivers. In 2011 the levee at Birds Point, MO was dynamited by the Corps of Engineers to protect a town that had declined to less than 3000 people, and destroyed valuable farmland in MO. See: https://www.thenewsstar.com/.../rising-waters.../82951014/ and:https://www.stltoday.com/.../article_3c73c9f8-74ff-11e0...
Carlton Crasher Still in use?
Dennis DeBruler The 1952 spans are still used by CN and Amtrak, http://bridgehunter.com/il/alexander/cairo-rr/

Photo from HAER ILL,77-CAIRO,1--1

Photo from HAER ILL,77-CAIRO,1--2

David Cantrell posted
Cairo, IL, 1913 Flood. Illinois Central Tracks, Lens towards Shawneetown and the railroad bridge.

Mary Rae McPherson posted
Two methods of steam transportation can be seen in this undated photo taken from the banks of the Ohio River at Cairo, Illinois.
The smoke from a northbound Illinois Central train can be seen approaching the Cairo Bridge on the Kentucky side as a sternwheeler makes its way upriver.
While the steelwork has been long replaced, it's something to consider that the piers holding up the bridge in this image remain in place to this day, still doing the job they were designed to do in the 1880s!
Mary Rae McPherson shared

Mike Chaotie shared William Shapotkin's post

William's comment on his post:

October 29 in railroad history: Cairo Rail Bridge. (From Larry Tennyson (via Joe Slezinger))

On this date in 1889, the Illinois Central Railroad began using a brand-new bridge over the Ohio River between Cairo IL and Wickliffe KY.

The Cairo bridge, which was designed by George Morison, was 3.5 miles north of Ohio River’s confluence with the Mississippi River.  Its main spans were two 518-foot pin-connected Whipple through trusses, the longest examples of this type ever built.

They were required to be 53 feet above the river’s high-water mark to provide clearance for steamboats.

The through trusses and adjoining deck trusses totaled 10,580 feet, making this the longest metal structure in the world at that time.  Including timber-trestle approaches, it was 20,461 feet long.  Total construction cost was $2.6 million—the most expensive bridge project yet undertaken in the United States.

Prior to this date in 1889, north-south traffic had to cross the river on a ferry boat.  After completing the bridge, ICRR possessed an all-rail route from the Great Lakes to the Gulf of Mexico.

Cairo Rail Bridge was replaced in 1952 by a new structure on the same site that re-used some of the original piers.  That bridge is still used today by Canadian National.

Dave Durham posted
Found this spectacular shot of Illinois Central train no.2, the New Orleans to Chicago Fast Mail crossing the Cairo Bridge circa 1910; can anyone provide info on those unusual signals? Unknown Photographer, Illinois RR and Whse Commission Report, Hathi Trust
Mike Spencer Signals were made by Hall Switch & Signal Company of Garwood, NJ. Properly they are called Banjos. They provided 2 aspects via means of a banner operated by an electromagnetic relay. The banner provided a daytime indication while a kerosene lantern provided a nighttime indication. C&NW and RDG were large users of this type of signal. Reading and C&NW photos will sometimes yield a Banjo or 2. I can think of maybe a dozen that have survived and are either in museums or collections. Illinois Railway Museum has (had?) one some years ago. There's another in Strasburg, PA at a museum. Hall made theirs of wood; Union Switch & Signal made something similar, called an Enclosed Disc Signal. One of those still survives at the Orange Empire Railroad Museum in CA. http://position-light.blogspot.com/.../hall-disc-aka...

David Daruszka commented on Dave's post
Banjo signal semaphore combination on the C&NW.
[I checked, and the building with the work "PICKLES" on it is not the Heinz plant that was south of Junction A-2. David Daruszka taught me this is looking northish at C&NW's Clybourn Station.]

The bridge is in the background of this 1901 photo.