It's a part of Duluth's history that can be found in countless photographs taken by locals and tourists alike.

And now it's gone.

You may not have noticed it yet - most people in town haven't - but part of the structure known as "Uncle Harvey's Mausoleum" or "the cribs," jutting out of the water of Lake Superior offshore from Canal Park, vanished sometime between New Year's Day and Valentine's Day.

It is - or was - a solitary concrete pillar that stood between the main "mausoleum" and shore. A photo shows it was standing as recently as Jan. 1. It isn't visible now. Waves, or ice, or both appear to have toppled the nearly century-old column, a remnant of a short-lived operation to unload sand and gravel. In more recent years, the ruins have been a popular destination for swimmers and divers in summer, and occasionally some ice explorers in winter.

Tom Deschenes, who works at Canal Park Brewing Company, may have been the first to notice the column was missing. He said he had been contemplating setting up a slackline - similar to a tightrope - between the cylinder and the larger structure, sometimes called the icehouse.

On Valentine's Day morning, as he biked to work, "I was thinking the timing was getting to be about right to set up the line," Deschenes recalled. "When I looked to the icehouse, the cylinder piece was gone."

As word of the fallen landmark made its way around social media in recent days, Duluth's Jim Richardson - an avid freediver who shoots underwater videos and posts them online as Lake Superior Aquaman; find them here - weighed in with his observations.

"It was only a matter of time," Richardson reported on Facebook. "The column was composed of timbers sheathed in concrete but much of the concrete below water level was eroded away, leaving bare wood."

The column also may have had a steel jacket at some point, Richardson said, based on his underwater observations. He said the water is about 12- to 14-feet deep in that spot, so the column probably is lying on the lakebed.

The icehouse may face a similar fate someday; it already has a list that has become more pronounced in recent years. Richardson said that his dives on the structure have revealed that the bottom crib is buckling in one corner. He said it doesn't appear to be in imminent danger of sinking further, but noted that someone with more engineering expertise would be needed to make an official determination.

Richardson said he plans to dive the area and get video of the fallen pillar this summer.

What was it?

So what was "Uncle Harvey's Mausoleum"? A historical marker placed by Visit Duluth along the Lakewalk tells the story:

"It is the ruins of an energetic but short-lived commercial enterprise by (the) Whitney Brothers of Superior," the marker reads. "It was Harvey Whitney's brainchild. ... The structure was the foundation of a sand and gravel unloading dock."

Some sources date the dock's construction to the winter of 1919, though an article in the News Tribune places the construction of the dock - or a similar predecessor on the same site - as early as 1917.

"The years following World War I were a busy time for Duluth construction, and Harvey was looking for ways to make his sand and gravel business more efficient," the Lakewalk marker reads. "Congestion in the canal and harbor slowed his barges, and he speculated that the city might revive efforts to rebuild the Outer Harbor Breakwater, which had once given this frontage some protection, but had been abandoned in 1872."

Sand and gravel were hauled to the dock by barges that were tied to the concrete "icehouse," which supported a steel hopper. Barge-mounted cranes unloaded the sand and gravel into the hopper, and a conveyor belt on a trestle moved the material to shore. The recently toppled column was the base for one of several supports for the trestle.

Harvey Whitney's gamble didn't pay off: The breakwater never was rebuilt, and it became untenable to keep unloading barges at the dock exposed to wind and waves. The dock was abandoned in 1922.

"He tried to deal with Superior on its terms, and lost," the marker reads. "It was his family that came up with the name 'Uncle Harvey's Mausoleum.' "

In the years since, the ruins have sparked a lot of stories, as the News Tribune's Chuck Frederick recounted in 2008:

"It was a prohibition-days casino, some argued. A fishing dock, others claimed. An ice house. Part of an old lighthouse.

"The former director of the Lake Superior Maritime Visitors Center, Pat Labadie, wrote in 2002, tongue planted firmly in cheek, that some believed the structure a fort, 'a bastion of defense erected there to protect Duluth residents from Badger State barbarians, from Michigan's mythical Yoopers or perhaps from Canadians.' "

If you know

Did you notice in recent weeks whether the pillar was still standing? Did you take a photo, and can you remember the date of your observation? Help us pinpoint just when the column fell. Send your observations to akrueger@duluthnews.com.

UPDATE: Duluth cribs mystery solved: Reader reports, photos pinpoint when column fell