Government (Arsenal) Bridge

Baltimore Through Truss Swing Bridge across Mississippi River
Rock Island, Rock Island County, Illinois
Davenport, Scott County, Iowa

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Name Government (Arsenal) Bridge
Built By Chicago, Rock Island & Pacific Railroad
Contractor Phoenix Bridge Company of Phoenixville, Pennsylvania
Engineer Ralph Modjeski
Currently Owned By Iowa Interstate Railroad Railroad
Length 1,854 Feet Total, 370 Foot Swing Span
Width 2 Tracks, 2 Vehicle Lanes
Height Above Ground 15 Feet to Normal Water Level
Superstructure Type Baltimore Through Truss with Pratt Through Truss and Steel Beam (Road)
Substructure Type Stone Masonry and Concrete
Date Built Opened 1896
Date Rehabilitated 1983 and 1997
Traffic Count 6 Trains/Day (Estimated)
Current Status In Use
IAIS Bridge Number 1822
Significance National Significance
Documentation Date September 2017

In 1852, the Chicago and Rock Island Railroad began construction of a 40 mile route from Chicago to the nearby city of Joliet.
With the first segment completed, the railroad continued constructing another 119 miles of track to Geneseo. By 1854, the remaining portions of track were constructed into Rock Island, Illinois; located on the Mississippi River.

The first bridge across the Mississippi River would be built connecting Davenport to Rock Island in 1856. After a fire and collapse later that year, the bridge was rebuilt and would begin carrying traffic into Iowa.
Later in 1856, the Mississippi and Missouri Railroad would begin construction on a pair of main lines in Iowa. One route went towards Missouri, while the other continued on the straight west trajectory.
The first 55 miles on the western mainline saw the connection of Davenport and Iowa City by the end of 1856. Another 31 miles to Marengo would be completed by the end of 1862.

These two railroads would become part of the Chicago, Rock Island & Pacific Railroad in 1866. The Rock Island later saw the completion of the route to Nebraska.

As traffic continued to build on the line, it was continuously upgraded. The route through Illinois was double tracked in the 1890s, and the route to Iowa City was double tracked by 1900.
However, this double track proved unnecessary and was removed in the 1930s. Because of the Rock Island Railroads poor management, the railroad oftentimes found itself in financial trouble; despite having a solid core of routes.
Between World War II and 1980, the railroad saw even harder economic downturns. Failed mergers and poor money management led to the inevitable downfall of the railroad.
By 1980, the railroad was officially bankrupt for the final time. Trustees saw the liquidation of the railroad, which sold off and abandoned many lines.

However, as this was the core main line of the Rock Island, it saw a positive future. After an earlier railroad failed in the early 1980s, the Iowa Interstate Railroad was formed in late 1984 to operate over track between Ottawa, Illinois and Omaha, Nebraska.
Since its original forming, the IAIS has turned a once dead mainline into a thriving alternative to Interstate 80. Today, this segment is known as the 1st Subdivision.

Perhaps the most famous railroad bridge across the Mississippi River is the Government Bridge, locally known as the Arsenal Bridge.
The bridge carries dual lanes of traffic and two tracks of Iowa Interstate Railroad on its 8 spans across the Mississippi.
Completed in 1896 and designed by chief engineer Ralph Modjeski, the US Army was in charge of the construction.
Also called the Rock Island Bridge, it connects to Rock Island Arsenal, a Government Installment.
The main span is 370 feet Long, and crosses part of Lock and Dam #15. This unique span can rotate a full 360 degrees.
This was also the site of the first railroad bridge across the Mississippi, built 1856.
In 1856, the bridge was hit by a steamboat which caused a span to collapse. A young Abraham Lincoln defended the railroad, and the later court case provided railroads with the opportunity to build more bridges across the Mississippi.

All the spans on this bridge are pin connected, with the exception of the vehicle approach on the west end. These spans vary in length.
In addition they all contain X frame portal Bracing. The difference is spans 2 through 7 are Baltimore Through Trusses with two decks, and 1 and 8 are railroad only Pratt through trusses. The eastern of these Pratt Trusses appears to be older than the 1896 date reported, and could possibly have used rebuilt parts.
As taken from the HAER documentation:

"The piers and abutments (see HAER Photo Nos, IL-20P-1, IL-20P-2, IL-20P-7, IL-20P-12, IL-20P-14) are constructed of limestone with sandstone facing. Abutments support each end of spans A and H; piers support the ends of spans 2 through 7 in the river, as well as the midpoint of span 7, the swing span. Except for the swing span pier, which is larger than the others, the various piers are relatively equal in size.

Spans 1 and 8 (see HAER Photo Nos. IL-20P-4, IL-20P-6, and IL-20P-20) serve as approaches to the bridge. They are substantially smaller and shorter than the other spans, rising from a level equal to the railroad bed. All other spans rise from a level equal to the lower vehicular road bed. The vehicular roadway has no approach spans, traversing only spans 2 through 7.

All trusses are tied at their top (see HAER Photo Nos. IL-20P-1, I1-20P-5, IL-20P-6, IL-20P-8, IL-20P-9, IL-20P-10, IL-20P-12, IL-20P-21, IL-20P-23, and IL-20P-24) with riveted steel members at each panel with diagonal cross members in each bay. A similar set of steel members (see HAER Photo Nos. IL-20P-11 and IL-20P-13) is used to tie the two sides together under the railroad deck and under the vehicular road bed. The control room (see HAER Photo Nos. IL-20P-1, IL-20P-5, IL-20P-8, IL-20P-9, IL-20P-18, IL-20P-19, and IL-20P-25), in the upper, center of the swing span, is reached from the vehicular roadway level by two, straight-run, open, steel stairs on the east side of the bridge, rising to the railroad track level with a shared steel deck landing, then continuing upward to the control room level. The room is surrounded by a narrow, steel walkway with a metal deck and pipe railing painted black. From the south walkway a steel cage ladder rises to a steel landing above the roof, which gives access to the steel ladder rising to the turntable for the upper swing span.

The control room is square in plan with a hipped roof covered with standing-seam copper roofing painted black. Roof, wall, and floor systems are all sawn wood members. There is a set of semi-circular metal gutters on all four sides of the roof. Decorative pressed-metal shingling painted black covers all four walls. The east elevation (see HAER Photo No. IL-20P-9) has a single doorway on its south end containing an original wood door with four lights over three panels and a modern raw aluminum storm door. To its north is a single window opening. Two single window openings are located on each of the south and west elevations. An octagonal bay window (see HAER Photo No. IL-20P-25) is centered in the north elevation with a single window opening in each of its three faces. All eight window openings contain one-over-one, double-hung, wood sash with plain interior and exterior, painted, wood casings.

The one-room interior (see HAER Photo Nos. IL-20P-18 and IL-20P-19) has wood floor covered with linoleum tile, overlaid with loose strips of carpeting. The walls are covered with horizontal, beaded, tongue-and groove, board siding. In the northeast corner is a pair of cabinets made of vertical, beaded, tongue-and-groove boards. In the center of the west wall is a wood shelf, dating from the original construction. The walls, cabinets, and shelf are all painted cream. The cabinets each have a set of three butterfly hinges and single latches. The shelf is supported by two decorative, cast iron brackets. The ceiling is acoustical tile attached to the original, tongue-and-groove, board ceiling. Near the south wall an inclined wood ladder leads upward to the ceiling hatch giving access to an unfinished attic used for storage. Lighting is by fluorescent and incandescent fixtures. There is an air-conditioning unit in the south window of the west wall. A modem electric heating unit supplies the necessary heat. An older electric heating unit survives along the west wall.

Along the south wall of the control room is an original, 550-volt, General Electric, motor-generator set, which converts alternating current to direct current in order to run a 50-horsepower motor, which, in turn, powers the drive train machinery for the swing span. A series of bull and bevel gears for the power train occupies the center of the room, surrounded by a polished brass guard rail (see HAER Photo Nos. IL-20P-18 and IL-20P-19). In addition to a control board on the north wall, the room also houses an alternating-current, motorized, direct-drive, air-compressor unit, which, at an undetermined date, replaced an original belt-driven unit. The air-compressor activates the pneumatic jacks underneath the swing span and the pneumatic rail locks on the railroad bed. The pneumatic system operates under 100 to 120 pounds per square inch of pressure, which is maintained by two original, riveted, steel, air-storage tanks located in the attic above the control room."

Complete coverage of it can be seen here:
HAER Documentation of Government Bridge
In addition, the photos can be seen below as well as on This Site

The author has ranked this landmark bridge as being nationally significant, due to the history and design of the structure.
Unfortunately, the bridge could be facing demolition in the near future. The state of Iowa has listed replacing this bridge as being a priority for the future.
The author considers this plan to be totally disregarding of history and significance of this bridge. Unfortunately, some of the most significant bridges in America crossed the Mississippi and Missouri Rivers, and have been removed.
The photo above is an overview from the Iowa bank. The photo below is a photo of the plaque. The bridge can be photographed from most any angle surrounding it.

Mississippi River Railroad Bridges
East (Sylvan Slough) IAIS Sylvan Slough Bridge
Upstream (Sylvan Slough) Sylvan Island Rail Bridge
Upstream (Main Channel) Clinton Rail Bridge
Upstream (Middle Channel) Willow Island Rail Bridge
Upstream (East Channel) UP Sunfish Slough Bridge
Downstream Crescent Bridge

These Pictures Start at Varying Points in the Series

Detail Pictures

Historic American Engineering Record Pictures


Source Type


Build Date Builders plaque
Contractor Historic Documentation
Railroad Line History Source ICC Valuation Information, Compiled by Richard S. Steele

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