Sylvan Slough Viaduct
Arsenal Road Mississippi River Crossing At Rock Island
Rock Island, Illinois

Sylvan Slough Viaduct

• Structure ID: NBI 000000000819904.
• Location: River Mile 482.9.
• River Elevation: 545 Feet.
• Highway: 24th Street, Arsenal Road.
• Daily Traffic Count: 8,900 (2003).
• Bridge Type: Steel Girder, Concrete Deck.
• Length: 604 Feet Overall, 82 Foot Longest Span.
• Width: 24 Feet, 2 Lanes.
• Navigation Channel Width: Non-Navigable.
• Height Above Water: 22 Feet.
• Date Built: Opened 1907, Redecked 1967.
This is one of three bridges connecting the Rock Island Arsenal to the mainland. The huge Govenment Bridge connects to Iowa, while this bridge, and another 3 miles upstream, connect to Illinois. While the Arsenal requires a vehicle pass to enter, one can cross the Mississippi River by using the Viaduct and the Government Bridge without having to enter the Arsenal or stopping at a checkpoint. This access may vary with threat level.

The first bridge built at this location was a wooden bridge built by the son of US Army Colonel George Davenport in 1863. They had received word that the government was planning to build a POW camp on the island, so they jumped at the chance to profit from that knowledge. The government did indeed buy the birdge in 1868, which almost immedieately failed when crushed by ice. The Davenports replaced the bridge with another wooden structure in 1872. The wooden bridge was replaced with a modern bridge in 1907. That bridge was rebuilt in 1967, with steel replacing the iron, and a concrete deck being installed.

Note that every other pier is angled out into the river current, built to break up any ice that builds up against the bridge piers.


Sylvan Slough Viaduct
Sylvan Slough Viaduct
Sylvan Slough Viaduct

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Photo and text by John A. Weeks III, Copyright © 2005, all rights reserved.
For further information, contact: john@johnweeks.com