The Civil War Ironclad That Sank in Minutes from a Historic Confederate Attack

The USS Cairo, Mississippi

They built the USS Cairo to be tough enough to take on Confederate forts along the Mississippi.

She had thick armor and heavy guns, but none of that helped when she hit something no one saw coming. Her sinking marked the start of a deadly new chapter in naval warfare.

This is the story of the ironclad that went down in history for all the wrong reasons.

The City-Class Ironclad

The USS Cairo entered service on January 25, 1862, under Flag Officer Andrew Hull Foote.

Named after Cairo, Illinois, it belonged to a family of seven “City-Class” ironclads built by industrial pioneer James Eads.

For Union strategists, these ironclads represented essential tools for controlling the Mississippi River—the key to splitting the Confederacy and securing victory.

Construction and Armament

Civil engineer Samuel M. Pook designed the Cairo, which James Eads constructed in just 100 days at Mound City, Illinois.

The term “ironclad” wasn’t figurative—the vessel featured 2.5 inches of plate armor, reinforced to 3.5 inches in critical areas with railway iron.

This protection rendered conventional weapons largely ineffective.

A steam-powered paddlewheel propelled the Cairo at 4 knots, while thirteen guns provided devastating firepower.

Military Service

Initially serving with the Army’s Western Gunboat Flotilla, the Cairo transferred to Navy control on October 1, 1862.

Its service record included the occupation of Clarksville (February 17, 1862) and Nashville (February 25), Tennessee, and engaging Confederate forces at Plum Point Bend.

The Cairo’s most notable achievement came during the Battle of Memphis on June 6, 1862. There, it joined a Union fleet that decisively defeated eight Confederate gunboats.

This victory enabled Union forces to occupy Memphis that very night, further tightening their strategic grip on the Mississippi River.

The Fateful Yazoo River Mission

On December 12, 1862, Lieutenant Commander Thomas O. Selfridge Jr. led the Cairo and other gunboats up the Yazoo River north of Vicksburg.

This mission formed part of the larger Yazoo Pass Expedition, a strategic attempt to attack Vicksburg from behind by clearing mines at Haines Bluff.

The flotilla moved in precise order: Pittsburg leading, followed by Cairo, Queen of the West, Signal, and Marmora.

As they navigated the murky, treacherous waters, approximately seven miles north of Vicksburg, Confederate shore batteries opened fire.

Selfridge immediately ordered his guns prepared and directed the Cairo to advance at full steam toward the enemy position, a decision that would seal the vessel’s fate.

The Sinking: A Historical First

As Cairo steamed toward Confederate positions, catastrophe struck without warning.

The first explosion tore through the port bow, creating a massive breach in the wooden hull beneath the armor.

Seconds later, a second blast hit near the middle section on the starboard side.

Water rushed in unstoppably, and the mighty ironclad sank in just 12 minutes to a depth of 36 feet. Remarkably, every crew member escaped without casualties.

This event marked a pivotal moment in naval warfare history: the first armored warship ever sunk by an electrically triggered mine.

Confederate Torpedo Technology

The “”torpedoes,” aka naval mines, that claimed the Cairo consisted of a 5-gallon glass demijohn filled with explosives, attached to a wooden float, and connected by wires to a shore-based battery.

Confederate officers Zedekiah McDaniel and Francis M. Ewing positioned these underwater weapons strategically in the Yazoo.

When Cairo approached, hidden volunteers completed an electrical circuit to detonate the mines, remarkably advanced technology for 1862.

The Search for Cairo

After sinking, Union forces concealed Cairo’s location by removing its protruding smokestacks and poles.

For nearly a century, the ironclad lay forgotten beneath accumulating Yazoo River silt.

In 1956, Vicksburg National Military Park historian Edwin C. Bearss and companions Don Jacks and Warren Grabau began a methodical search using historical maps and a simple pocket compass.

They discovered that certain river spots caused compass needles to deviate dramatically, indicating large iron masses below.

In 1959, divers finally retrieved armored port covers from the site.

The 1964 Salvage Operation

With funding from Mississippi, Warren County, and local fundraising efforts, an ambitious salvage operation commenced.

Recovery teams developed a plan to raise the Cairo intact by sinking a barge into the riverbed depression and lifting the ironclad onto this platform.

The October 1964 attempt ended in partial disaster. The three-inch cables cut deeply into the century-weakened wooden hull, causing the strained cables to snap and breaking the vessel into three large sections.

The team pivoted to salvaging the Cairo in pieces. By December 1964, all three sections had been successfully placed on barges and towed to Vicksburg.

Preservation and Restoration

The Cairo’s sections were transported to Ingalls Shipyard in Pascagoula, Mississippi, for extensive conservation work, including ear syringes and tourniquet clamps.

Workers carefully removed, cleaned, and stored the iron armor plates.

They disassembled, cleaned, and reassembled the dual steam engines to remove river sediment and corrosion.

On September 3, 1971, the USS Cairo earned official recognition on the National Register of Historic Places.

Finally, in June 1977, the vessel reached its permanent home at Vicksburg National Military Park, reconstructed on a concrete foundation near the National Cemetery.

The USS Cairo Museum Today

Located at 3201 Clay Street and open daily from 8:30 am to 4:30 pm, the museum offers an immersive glimpse into Civil War naval history.

The exhibits display a fascinating array of artifacts, such as mess utensils, personal effects from shaving gear to leather shoes, and various tools including pulleys and blacksmith implements.

The weapons collection features muskets and pistols carried by crew members.

The Cairo itself rests under a modern tension-fabric shelter that replaced the original protective covering, allowing visitors to view the ironclad from multiple angles.

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