Clinton Rail Bridge

• 1857: 44 miles completed from Clinton to Wheatland, Iowa by the Chicago, Iowa and Nebraska Railroad
• 1858: 20 miles completed from Wheatland to Lisbon, Iowa by the Chicago, Iowa and Nebraska Railroad
• 1859: 17 miles completed from Lisbon to Cedar Rapids, Iowa by the Chicago, Iowa and Nebraska Railroad
• 1861: 41 miles completed from Cedar Rapids to Belle Plaine, Iowa by the Cedar Rapids and Missouri River Railroad
• 1861: 41 miles completed from Cedar Rapids to Chelsea, Iowa by the Cedar Rapids and Missouri River Railroad
• 1862: 29 miles completed from Chelsea to Marshalltown, Iowa by the Cedar Rapids and Missouri River Railroad
• 1864: 29 miles completed from Marshalltown to Nevada, Iowa by the Cedar Rapids and Missouri River Railroad
• 1865: 29 miles completed from Nevada to Boone, Iowa by the Cedar Rapids and Missouri River Railroad
• 1867: 150 miles completed from Boone to Council Bluffs, Iowa by the Cedar Rapids and Missouri River Railroad
• 1867: 6 miles completed from Missouri Valley to California Junction, Iowa by the Cedar Rapids and Missouri River Railroad
• 1884: CI&N and CR&MR officially acquired by Chicago & North Western Railway
• 1887: 6 miles completed from Beverly to Otis, Iowa bypassing Cedar Rapids by the Linn County Railway
• 1887: Linn County Railway acquired by Chicago & North Western Railway
• 1891-98: Second track constructed between Clinton and Cedar River
• 1898-1900: Second track constructed between Cedar River and Mashalltown
• 1898-1901: New alignment completed between Boone and Ogden, Iowa; including the Des Moines River Bridge
• 1900-02: Second track constructed between Marshalltown and Council Bluffs
• 1933: Old route via Moingona between Boone and Ogden abandoned
• 1995: Chicago & North Western purchased by Union Pacific Railroad
• 1995-Present: Union Pacific operates the Clinton Subdivision between Clinton and Boone
• 1995-Present: Union Pacific operates the Boone Subdivision between Boone and Missouri Valley
• 1995-Present: Union Pacific operates the Omaha Subdivision between Missouri Valley and Council Bluffs

Located between Iowa and Illinois, the Clinton Swing Bridge is one the heaviest used railroad bridges across the Mississippi. The swing span is the largest ever erected, and it was the first electrified swing bridge.
When built, the bridge replaced an older single track bridge. That bridge contained several spans, mostly mismatched Pratt Trusses that would later be relocated to Fall River and Lawrence County, South Dakota.
This bridge currently contains four spans. A deck girder span, a Swing Span, a Parker Through Truss span and a Quadrangular Through Truss Span.
The Parker Through Truss contains 7 panels with riveted connections, the Quadrangular Span has riveted connections and the swing span has a pair of 8-panel leafs with riveted and pin connections.

Blueprints of the bridge, from Railroad Gazette: Volume 48 Issue 2

Unfortunately, the bridge is scheduled to be replaced in 2022, with demolition occurring by 2025.
As a result, this bridge is almost certainly bound for destruction when the new bridge opens, approximately 100 feet to the south. Construction on a new bridge begins in 2021, and the old crossing will be removed in 2025.
The bridge sits on all masonry substructures. The abutments are extra wide for a third track, which was where the old bridge sat.
During the first decade of the 20th Century, the C&NW engineered several trusses of their own and had them fabricated. The main span of this bridge was one of them.

Historic photo of the previous bridge

While not the oldest bridge across the Mississippi River, the series of three bridges which makes up this crossing is one of the largest. As a result, the author has ranked it as being of high significance, due to the unique design, massive size and old age.
The photo above is an overview. The photo below is sway bracing on the swing span.