On this day in 1918, a U.S. Navy ship failed to arrive in Baltimore as scheduled.
No trace of the ship has ever been found. To this day, it remains a complete mystery, and the largest unexplained loss of life in U.S. Naval history (306 passengers and crew)
The ship was the collier U.S.S. Cyclops. A collier was a ship designed specifically to carry coal (the 1918 equivalent of an oil tanker), though on the last trip she had a cargo of manganese ore. The Cyclops was a reasonably large ship, 542 feet long (165m) and just under 20,000 tons. And she vanished without a trace.
The ship was en route from Brazil to Baltimore when she disappeared. Much has been made over the captain's (George Worley) health & temperament, and his possible pro-German leanings (this was during World War I) but nothing has ever been substantiated. An extensive check of German archives after the war turned up no evidence of the ship having been sunk or captured by hostile action.
Realistically, the ship likely sank in a storm, or due to major structural failure. I'm not a believer in the Bermuda Triangle or more exotic theories of things that vanish. Lawrence Kusche, in his excellent 1975 book "The Bermuda Triangle Mystery Solved" postulated a storm sinking the ship, which already had known mechanical problems.
In 1968 diver Dean Hawes reported finding wreckage of a ship that matched the Cyclops description off Norfolk. Subsequent attempts to locate this wreck have been unsuccessful. And there have been several.
There are a handful of mysteries I'd love to see solved in my lifetime. This is one of them.