Portland Harbor’s Hidden Mines and Darkened Lighthouses
When the USS Maine blew up in Havana Harbor in February 1898, America got ready for war. Soon after, Portland Harbor went dark.
The Army Corps of Engineers filled the waters with hidden mines, then shut off Spring Point Ledge Light and Portland Head Light for three months.
These mines linked to shore stations where soldiers waited to push buttons that would blow up any Spanish ships that tried to sneak in. Portland wasn’t alone – 28 major U.S. ports got the same treatment.
The lights came back on July 26, 1898, as the war wound down.
Today, you can walk the 900-foot granite breakwater to Spring Point Light and picture a harbor once rigged to explode.
The USS Maine Blew Up and America Got Mad
The USS Maine exploded in Havana Harbor on February 15, 1898, killing 266 American sailors. American newspapers quickly blamed Spain, though nobody knew what really caused the blast.
“Remember the Maine! To Hell with Spain!” became the battle cry across the country.
Newspapers ran wild headlines that pushed President McKinley toward war with Spain, even though he didn’t want to fight at first.
Army Engineers Planned Harbor Defenses Years Earlier
In 1885, the Endicott Board created plans to protect American harbors with modern defenses, including electric underwater mines.
Portland, Maine became a major harbor defense site around 1895 as part of this nationwide system.
The Army Corps of Engineers worked on the technology for these mines, which used underwater cables connected to shore stations. They built mine facilities at major ports but kept the mines in storage until needed.
War Started After Months of Tension
President McKinley asked Congress to help Cuba on April 11, 1898, after months of growing tensions. Congress passed a resolution on April 20 telling Spain to leave Cuba or face consequences.
The Navy started blocking Cuba the very next day.
Four days later, on April 25, Congress officially declared war, which they backdated to April 21 to cover the blockade that had already begun.
Portland Harbor Got Mined Almost Overnight
When war broke out, the military rushed to protect American harbors from possible Spanish naval attacks.
Army engineers planted underwater mines in 28 major U.S. ports, with Portland Harbor high on the list because of its busy East Coast shipping traffic.
Teams worked nonstop to set up the mine systems, bringing in special equipment and trained workers.
Famous Lighthouses Went Dark for Safety
Spring Point Ledge Light and Portland Head Light stopped shining in early 1898 and stayed dark for about three months during the war.
Military officials knew Spanish warships might use these beacons to safely enter the harbor at night.
The lighthouse blackout came with strict rules against nighttime ship movements in Portland Harbor because of the danger from underwater mines.
Underwater Bombs Waited for Spanish Ships
The mines sat anchored to the harbor bottom at depths from 20 to 250 feet, creating an invisible barrier against enemy ships.
Each bomb connected to shore through underwater electrical cables that ran to control stations. Military operators watched the harbor day and night, ready to push the button if Spanish warships showed up.
Special boats placed these weapons throughout the harbor.
Portland’s Busy Harbor Made It a Target
Over 500,000 passengers moved through Portland Harbor each year, making it one of the East Coast’s busiest ports. Seven major steamship companies regularly brought goods, coal, food, and people through the harbor.
The military already had troops at Fort Preble, Fort Scammel, and Fort Gorges, which helped protect the harbor alongside the new mine system.
Soldiers Stood Ready to Blow Up Enemy Ships
Control buildings lined the shoreline, where soldiers tracked ships and stood ready to set off mines under enemy vessels. The Army kept boats busy checking and fixing the mines.
They stored extra mines and TNT in special torpedo buildings near the harbor.
Teams regularly tested the electrical cables to make sure the mines would actually explode when needed.
The Spanish Navy Never Showed Up
Spanish naval forces focused on protecting their Caribbean colonies instead of attacking the American mainland.
Admiral Dewey’s American fleet destroyed the Spanish Pacific ships at the Battle of Manila Bay on May 1, 1898. Meanwhile, the Spanish Caribbean fleet got trapped in Santiago Harbor by the U.S. blockade in Cuba.
When Admiral Cervera finally tried to break out on July 3, American ships destroyed his entire fleet.
Lighthouse Beacons Returned in Late July
Both Spring Point Ledge Light and Portland Head Light started shining again on the evening of July 26, 1898, after three months of darkness.
By then, Spanish naval power had been crushed in both the Caribbean and Pacific, making harbor attacks extremely unlikely.
Ships could once again navigate safely into Portland at night with the familiar lighthouse beacons guiding their way.
Though the mines stayed in place, the strict navigation rules gradually loosened as the threat level dropped.
America Became a World Power in Just 114 Days
An armistice signed on August 12, 1898 stopped the fighting after just 114 days of war. The Treaty of Paris made it official on December 10, 1898, ending the Spanish-American War for good.
Spain gave up Cuba, handed over Puerto Rico and Guam, and sold the Philippines to the U. S. for $20 million. The United States suddenly found itself with an overseas empire, while the once-mighty Spanish empire collapsed.
The war that started with harbor mining in places like Portland ended with America stepping onto the world stage as a major power.
Visiting Spring Point Light, Maine
Spring Point Light at 2 Fort Road on Southern Maine Community College campus tells the story of when the U. S. Army Corps of Engineers planted submarine mines in Portland Harbor during the Spanish American War in 1898.
The lighthouse went dark for three months to keep Spanish ships from using it for navigation.
You can tour the lighthouse interior for $5 on Tuesdays, Thursdays and every other Saturday from 11am-2pm starting July 1st, 2025, plus explore historic Fort Preble ruins for free.
This article was created with AI assistance and human editing.
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