Marvin Barrash, of Kent Island, Maryland shows the displays he made with photos of the lost USS Cyclops. The Navy ship vanished 100 years ago with 309 men aboard, and it remains the greatest loss of life unrelated to combat in U.S. Navy history. (Tim Prudente/ Baltimore Sun)

There should have been a clue: a distress call on the radio, a shard of wooden lifeboat, even a sailor’s cap. How could 309 men and their ship, a naval vessel bigger than a football field, just vanish?

One hundred years ago Tuesday, the USS Cyclops was due to steam up the Chesapeake Bay and dock in Baltimore at what is now Port Covington.

The ship still hasn’t shown up.

Its eerie absence is an enduring mystery, fueling fantastical theories of the Bermuda Triangle, giant squids and German spies. The truth is, no one knows what became of the Cyclops or its crew — sailors such as Thomas Lee of West Baltimore; Adam Siewierski of Canton; and Burt Asper, a doctor who practiced at Sheppard Pratt.

There was no ceremony for them Tuesday. Memories of the Proteus-class collier — it hauled coal — have faded. The only known monument to the ship is a plaque that hangs in France.

And yet, in this era of high-tech discovery — when explorers have found a World War II cruiser sunk in the Philippine Sea and an aircraft carrier lost in the Coral Sea, when forensic anthropologists conclude that bones found on a Pacific island probably belonged to the missing aviatrix Amelia Earhart — the old hope returns that the Cyclops might be found.

“In terms of loss of life and size of ship, it’s probably the last great mystery left unresolved,” said James Delgado, the renowned underwater explorer.

Built in Philadelphia, steel-hulled and immense, the Cyclops splashed in as the Navy’s biggest, fastest fuel ship. About 540 feet long, 65 feet wide, the ship could haul 12,500 tons of coal and steam 15 knots. Its winches could send 800-pound bags of anthracite along cables. Huge clamshell buckets could lift two tons of coal in a single mouthful.

“A monster collier,” newspapers called it. “A floating coal mine.”

Launched in May 1910, the ship was designed to refuel the Navy fleet — work both grueling and dangerous. The coal in the cargo hold was prone to catching fire. Cables snapped. Bucketfuls tumbled to the deck.

The sailors steamed out of Norfolk and down the Atlantic Coast to U.S. bases in Cuba, Haiti and Puerto Rico.

With U.S. entry into World War I in April 1917, the Cyclops, outfitted with 50-caliber guns, delivered doctors and medical supplies from the Johns Hopkins Hospital to Saint-Nazaire, France.

Months later, the ship arrived in Brazil to load 10,000 tons of manganese ore. Denser and heavier than coal, the ore for steelmaking was unfamiliar cargo for the crew. The heavily laden vessel voyaged to Barbados, resupplied for nine days at sea, then steamed off for the steelyards of Baltimore. It was March 4, 1918.

The Cyclops was never seen again.

The search was exhaustive: Navy cruisers scoured the trade routes, scouted the beaches, inspected remote bays. Crews radioed the lost ship day after day, but nothing — no reply, no debris, not even an oil slick. Out in the West Indies, the ship had vanished.

In June 1918, then-Assistant Navy Secretary Franklin D. Roosevelt announced the ship and its 309 men were presumed lost at sea. It was the greatest loss of life unrelated to combat in U.S. Naval history.

“There has been no more baffling mystery in the annals of the Navy than the disappearance last March of the U.S.S. Cyclops,” Navy Secretary Josephus Daniels wrote. “There has not been a trace of the vessel, and long-continued and vigilant search of the entire region proved utterly futile.”

Speculation swirled. Could the heavy ore have ruptured the hull, sinking the ship instantly? Did the unfamiliar cargo leak fumes that poisoned the crew? U-boat torpedoes could have sunk the ship, but where was the debris? Rough seas could have swamped it, but there was no storm,and no distress call. German raiders could have captured the ship, taken the crew hostage and steamed home with their prize, but the Cyclops lacked fuel for a transatlantic voyage.

Wilder theories emerged of sea monsters, mutinies and meteorites. The loss of the Cyclops — along with the later disappearance of five Navy torpedo bombers known as “Flight 19” — gave rise to the ship-swallowing lore of the Bermuda Triangle, a myth roundly debunked today.

Still, there were no answers for the families of the Baltimore sailors — seamen such as Charles Holmes, who left behind a wife and infant son on Presbury Street; Edward Dresbach, who wrote cheerful letters to his mother on Harlem Avenue; and Beverly Jones and Herbert Price, two city boys just 17 years old.

Today, only scattered reminders speak of them. At Baltimore’s Loudon Park Cemetery, one gravestone reads: “T. Vernon Lee, lost on the U.S.S. Cyclops.” In Baltimore’s War Memorial, their names are inscribed in marble with those of other Marylanders killed during WWI. And in Halethorpe, an American Legion post bears the name and photo of one sailor, Dewey Lowman.

Little is known about the 19-year-old from Arbutus, a firefighter aboard the Cyclops.

“People have asked me over the years; I can’t really tell them much,” said Edgar Lowman, of Halethorpe, his 86-year-old nephew.

Fifteen Marylanders disappeared with the ship, most of them young men without wives or children.

The loss became a discomfiting episode for the Navy, says Marvin Barrash of Kent Island, the great-nephew of another ship firefighter.

“The whole existence of the ship has been swept under a rug,” he said. “It wasn’t like it was lost in a glorious battle. It just kind of fell off the face of the Earth.”

Barrash spent more than a decade researching the Cyclops, amassing Navy records, ship logs, dispatches, photos, even a sooty bag of manganese ore. In 2010, he published a 700-page history of the ship. Now, he’s working with the office of U.S. Rep. Andy Harris ­to erect the Cyclops’s first monument.

“As a Navy veteran, I feel I have a duty to honor the crew members on the USS Cyclops who never returned home to Baltimore, and the families they left behind,” the Baltimore County Republican said in a statement.

Barrash believes a cascade of failures doomed the Cyclops. One of two engines broke. The ship was unbalanced by the heavy ore. At night, with the deck battened down and crew asleep, a big wave rolled the Cyclops. The huge collier, Barrash figures, eludes explorers because it sank into the Puerto Rico Trench, the deepest part of the Atlantic. The trench cleaves the ocean floor across nearly 1,000 miles.

“I just want her to be found,” Barrash said. “I want the 309 to be at rest, as well as the families. It’s something everybody needs: some resolution.”

Underwater explorers have dived for the prized wreck for decades, but a succession of recent, splashy discoveries brings renewed hope to the hunt. Today’s crews employ devices that can detect the magnetic field of a washing machine buried in sea mud. Their sonar can sweep the depths like a flashlight. Year after year, the number of shipwrecks still lost dwindles.

“The shortlist keeps getting shorter these days as technology steps in,” said Delgado, the explorer. “Things can be found. It’s just a question of time and money.”

Delgado and researchers from the National Oceanic and Atmospheric Administration announced two years ago that they had found the Baltimore-built tug USS Conestoga, missing since 1921, outside San Francisco Bay. A research crew led by Microsoft co-founder Paul Allen said last August that it had found the USS Indianapolis, a Navy cruiser torpedoed in the Pacific late in World War II. Last week, Allen’s crew said it had found another vessel beneath the Coral Sea: the World War II aircraft carrier USS Lexington.

These deep-pocketed, well-equipped research crews haven’t taken on the hunt for the Cyclops — at least, not publicly. But solo explorers sometimes write Barrash, believing they have found the ship.

A Navy diver thought he located it off Virginia’s coast in the late 1960s. Bad weather forced him up, and crews never found the wreck. Excitement grew over a wreck upside down off Florida’s coast, but it turned out to be a German fuel ship from World War II.

A treasure hunter in the Dominican Republic sent Barrash photos last year of a newly discovered shipwreck. The Cyclops was found, this diver declared. Barrash noticed the doorknobs bore markings from Glasgow and the dishes showed European crowns.

Out there, somewhere, the great collier remains.

— Baltimore Sun