The Mystery of South Marin Island

by Brian Crawford

Detail from Tide Lands Map showing South Marin Island. Anne T. Kent California Room Collection

I work as a volunteer at the Anne. T. Kent California Room annex, where a large number of priceless historic maps of Marin County are stored. I have the greatest job for a historian. I must study each map, identify its location, record its characteristics, and try to date it. For many of the maps, of course, this is fairly straightforward because the location, surveyor, date, scale, etc. are written on the map. But these aren’t the official maps registered at the County — most of these are the surveyor’s working copies, half-finished drafts, and sometimes mere sketches. Many have no labels at all. I have to try to identify one or two features on the map, then use Google Earth to attempt to match up a bit of road or an unusual hill or a bend in a creek. As you can imagine, this can take a while. Tedious, right?

But many of the maps contain information not available elsewhere, such as the placement of buildings long demolished, the names of every lot owner in a town, or an earlier alignment of a road or waterway. These maps may be the only record of how things once were.

This is especially true of the bay shoreline. In the 19th century, much of the eastern fringe of Marin consisted of marshlands. That didn’t stop developers, and many maps show streets and lots right across the marshes and even well out into the bay. People would buy these lots, then haul fill from other sites to raise them enough to build on.

South Marin Island on 1873 map of Marin by Hiram Austin. Anne T. Kent California Room Collection.

One day I pulled out a map titled only “A-11–8a: Tidelands Map №8.” It showed the shore of San Rafael Bay from Point San Pedro to Point San Quentin, with San Rafael Canal cutting diagonally across it, so it was easy to locate. San Rafael Bay is shown covered with a grid of lot lines, almost two square miles of submarine real estate.

I started recording the notable features: Point San Quentin, the Canal, and of course the Marin Islands: East, West and… South?

Wait, what? I’ve sailed and kayaked that bay for decades. The water is not deep, rarely more than ten feet, but it is unbroken. I could draw you sketches of East and Marin Islands, but I know for a fact there is no such thing as South Marin Island. Yet there it is, clearly marked and labeled. I stared at it in disbelief. Maps certainly can and do contain errors, but this was no slip of the pen. Looking closely, I could see that there were survey points on the island — someone had actually landed on it and measured five corners of the little islet. Clearly, a third island had existed there at one time.

There was no indication as to who drew it or when, but other clues indicate it was made between about 1890 and 1910. I was thrilled — like Columbus, I had discovered a new land. I couldn’t wait to tell my sailing and kayaking buddies. I knew I could win a beer with the answer to the question, “How many Marin Islands are there?”

But what happened to the island? I knew a number of islands in San Francisco had been blown up as hazards to navigation: Blossom Rock, Arch Rock, Harding Rock, and Shag Rock, for instance. But San Rafael Cove was always too shallow for navigation for any but small boats and the island wasn’t on the course between any ports.

I consulted with my cadre of local history experts at the annex. None of them had ever heard of South Marin Island. Every online reference to the Marin Islands calls them a pair of islands. A Google search for “South Marin Island” turns up some old references to it, saying it was also known as San Rafael Rock and Murphy’s Rock. Murphy could refer to Don Timoteo Murphy, the first Anglo resident of San Rafael, but I can find nothing else about either name. But what happened to the island?

My online research was stymied. I looked up in frustration and my eyes fell on Hiram Austin’s magnificent 1873 map of Marin hanging on the wall opposite. I went up close, and sure enough, there was the island. All of us in the annex had studied that map many times, but none of us had noticed it. Of course, it was easy to miss unless you were looking for it.

I moved to the map right next to it, George Dodge’s 1892 map of Marin, another map with which I was very familiar. At first I thought it was missing, but then I noticed a tiny unlabeled O hidden in a row of X’s marking a property line, like the X’s and O’s at the end of a love letter. It could only be the island. I couldn’t shake the feeling that someone had snuck into the archives and inked in the rock on every map of the bay.

Long-time surveyor Ed Nute was able to provide an aerial photograph from 1952 which showed what may the last photograph of the island. Also prominent is the streaming outfall from the sewage treatment plant in the days before the EPA.

Detail from a 1954 aerial photo showing South Marin Island. Anne T. Kent California Room Collection.

Then I looked at the next item on the wall, not an arm’s length away from where I had worked for two years. It was a huge blown-up aerial photograph of Marin from 1954. Surely the island wasn’t there in 1954.And yet there it was, clear as day, right where the old map said it should be. But the photo also clarified the fate of the island. Two long dikes had been built out to the island — one stretching off to the southeast to the Marin Rod and Gun Club on Point San Quentin; the other running southwest toward Kerner Boulevard. The dikes enclosed a large area of marsh and shallow water, which was later filled and developed. The island is just outside the corner of the “reclaimed” land. In the photograph, the enclosed polder is still being drained, so the dikes were still new or under construction in 1954.

So where is the island today? I overlaid the old map onto Google Earth to confirm my analysis, and it matched up perfectly. South Marin Island was still there, incorporated into the dikes. A third dike has now been added, running east from the island and curling around to the north to Pickleweed Park. The series of dikes is now called the Shoreline Trail, part of the San Francisco Bay Trail. No wonder I had never seen the island — I try to avoid dikes when sailing.

Looking towards West & East Marin Islands from the site of South Marin Island (today’s Bay Shore Trail). © Brian Crawford

I did some Googling for the various names for the island and learned that it had once been a heron rookery, as West Marin island still is, and a favorite place for duck hunters. I was surprised to discover that a tragedy had occurred on that remote speck of rock.

On Sunday, October 29th, 1922, two young men, Fred Scheuman and his brother-in-law Al Nauert, rowed out in a skiff to hunt ducks on Murphy’s Rock. It was a gusty day and the bay was choppy. They saw another boat with two other duck hunters in it a half mile farther out in the bay, obviously struggling with the waves. Suddenly they saw the boat overturn. Scheuman, who was an expert oarsman, jumped into the skiff to rescue them. Nauert, who was not as handy in boats, remained on the rock. He saw Scheuman row frantically to the overturned boat and the men floundering in the icy water. Due to the distance and the rough water, he could not make out exactly what happened. No doubt the men in the water tried to climb aboard Scheuman’s skiff and overturned it in their panic. Nauert could see the skiff drifting away upside down with a man clinging to the keel. Then all three men disappeared from sight.

Marooned, Nauert spent some long cold anxious hours on the rock, until his shouts attracted the attention of a passing rowboat and he was picked up and taken to shore. He notified the sheriff and the coroner and a search was made for the missing men. But it was not until Wednesday afternoon that all three were recovered. The other two men lost, Enrico Allegrini, 22, and Albert Martignoni, 25, had taken a man’s boat without his permission. The brave Fred Scheuman who died trying to save them was a 28-year-old accountant and left a young wife and a three-year-old daughter.

Originally published at



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Anne T. Kent California Room

Anne T. Kent California Room

The official Medium account of the archive of Marin County history & culture at the Marin County Free Library