Oyster shells: Petaluma’s ‘Secret Sauce’

On the evening of September 9, 1909, Gunerius Aanunsen sailed up the Petaluma River on his schooner the Fearless with a cargo of oyster shells, docking at his supply yard beside the D Street Bridge. Returning the next morning, he found the boat submerged. During evening low tide its hull, weighted by the shells, cracked on a hidden silt mound.

The sinking of the Fearless illustrated the perils of using a tidal estuary as a shipping channel. The genesis of Petaluma’s founding, the waterway came with a congenital birth defect — instead of flowing like a stream, it rose and fell with the ocean tides twice each day, making it prone to silting up.

At the time of the mishap, only the Sacramento and San Joaquin rivers exceeded the estuary as a waterway for shipping commercial tonnage in California. Two steamers and more than 60 flat-bottomed schooners plied its 18 miles to and from San Pablo Bay with an annual 200,000 tons of goods, including 100 million eggs, Petaluma’s new agent of wealth as the self-proclaimed “Boss Chicken Town of the Pacific Coast.”

But with economic prosperity came more silt.

The expansion of farmlands led to the elimination of wetlands and the rechanneling of tributary streams, sending erosion from the plowed fields into the estuary during rainy seasons, where it trapped boats like the Fearless in its muddy grasp.

Having a clogged artery at the heart of town raised the perennial question, according to local historian Skip Sommer, as to whether Petaluma wanted to be known as a river town or a mud town. For more than a century, the answer turned on the secret sauce of the Boss Chicken Town — oyster shells.

The arrival of oyster shells coincided with the Army Corps of Engineers’ first dredging of the estuary in 1880. Petaluma previously funded two dredgings of the upper channel north of Haystack Landing in 1859 and 1866, along with cuts made by ferryboat operator Charles Minturn. The arrival of the San Francisco and North Pacific Railroad in 1870 however made dredging an existential imperative.

Having bypassed Petaluma, the railroad created its own shipping terminus on the estuary south of town near Lakeville. Fearing a transportation monopoly, local business leaders successfully lobbied Congress in 1880 for $28,000 — or $875,000 in today’s currency — to have the Army Corps dredge the estuary and re-channel some of its 80 serpentine bends.

The dredging coincided with the invention in Petaluma of an efficient egg-hatching incubator by Isaac Dias, a dentist from New Orleans. He was later joined in perfecting and marketing it by one of his patients, Lyman Byce.

In 1880, Christopher Nisson, a Danish immigrant, purchased one of Dias’ incubators and employed it to launch the country’s first commercial egg hatchery on his ranch in Two Rock. The one ingredient Nisson lacked in his transformation of the chicken from pastoral farm animal to egg assembly line was calcium. If his hens were to dramatically increase their egg production, they needed many times their natural amount of calcium to avoid brittle bones and soft-shelled eggs.

For a calcium supplement, Nisson turned to oyster shells.

Crushed oyster shells were already being used in feed for backyard chickens, but not on the industrial scale he envisioned. Fortunately for Nisson, large mounds of ancient oyster shells, or middens, had been preserved beneath the waters of the South San Francisco Bay near San Mateo, built up by indigenous tribes over thousands of years.

In 1880, Nisson persuaded Petaluma grain merchant George P. McNear to ship oyster shells up the estuary from the South Bay. The shells enabled him to quickly increase his flock to 2,000 hens, and begin selling incubated baby chicks to his neighbors. Within a decade, six additional hatcheries were operating in Petaluma, drawing hundreds of aspiring chicken ranchers to the area.

Gunerius “George” Aanunsen immigrated to San Francisco from Norway in 1889. At the turn of the century, he and his brother Pete opened a supply yard in Petaluma for oyster shells, coal, and wood at the southwest corner of the D Street Bridge. The brothers dissolved their partnership un 1907, with Pete retaining the coal and wood supply business while Gunerius opened the South Bay Shell Company on the southeast side of the D Street Bridge.

The site would remain an oyster shell facility for the next 110 years.

The opening of Aanunsen’s new shell yard coincided with the third major dredging of the estuary by the Army Corps, the second having taken place in 1892. In the River and Harbor Act of 1904 Petaluma was provided a $7,500 ongoing annual appropriation for dredging ($234,000 in today’s currency). The Army Corps recommended accumulating the annual allocation to fund a thorough dredging of the channel every four or five years.

But, as the Fearless’ sinking demonstrated just two years later, Petaluma couldn’t wait that long. After only one or two heavy rain seasons, enough silt filled the estuary’s upper channel to make it a mud trap for vessels at low tide. As a result, the annual funding allocation was eaten up by regular maintenance dredging. The exception was the River and Harbor Act of 1930, which allocated $200,000, or $4.4 million in today’s currency, to fully dredge and straighten parts of the estuary to Cloudy Bend.

1930 also saw Aanunsen’s retirement from the oyster shell business. After resurfacing the sunken Fearless, he converted it into a sloop-rigged barge, purchasing a tugboat to pilot it up and down the creek. The tugboat also served as his home. For the next 30 years, he helped keep the Boss Chicken Town supplied with shell as annual egg production soared to half a billion eggs.

At the age of 67, Aanunsen set sail for the San Diego Bay, where he devoted a year to collecting sea shells for museum collections before his body was found floating in the bay, the apparent victim of an unsolved murder.

Aanunsen’s shell yard beside the D Street Bridge changed hands a few times before being purchased in 1948 by the Pioneer Shell Company, which constructed a processing plant on the site capable of crushing 10 to 12 tons of oyster shell an hour. By then, oyster shells were being used not only for poultry feed, but horse feed, fertilizer, and landscaping.

Other shipments on the estuary were decreasing however, due to the rise of trucking and the demise of Petaluma’s chicken industry. After World War II, more efficient caged factory farms were springing up around the county, putting the area’s small chicken ranches out of business.

In an attempt to turn the tide, Petaluma presented Congress with two bold proposals. The first was a name change for the estuary from the Petaluma Creek, which it was commonly called, to the Petaluma River. Contrary to popular lore, the name change was not required to maintain federal funding for the dredging. Instead, Petaluma believed that “river” would carry more prestige than “creek” in helping the town attract new river-dependent industries.

The second proposal, which carried a price tag of $6.5 million ($58 million in today’s currency), called for a major reengineering of the estuary in hopes of attracting new commercial traffic and also recreational boats. Congress quickly passed the name change in 1959, but the reengineering proposal was eventually ruled out as cost prohibitive.

The city succeeded however in attracting a handful of enterprises that used the river for transporting heavy construction materials like gravel and concrete. Together with the oyster shell plant, then owned by Jerico Products — who diversified to also transporting sand for construction — there was sufficient commercial tonnage to qualify for continued dredging by the Army Corps.

After the Corps’ dredging in 2003, the Petaluma River was classified as a “low use” waterway, placing future dredging in jeopardy. At that time, barge traffic was largely dependent on just two companies — a concrete plant and the oyster shell plant.

In 2006, the concrete plant closed, leaving only oyster shells to justify future dredging.

It wasn’t enough.

Lind Marine, the new name of Jerico Products, steadily reduced the tonnage of shells and sand on their barges to navigate the increasingly shallow channel until 2017, when it proved no longer profitable to do so. By then, river traffic consisted almost entirely of recreational boats which, while contributing tourism revenues to the city, didn’t figure into the Corps’ criteria for dredging. By 2020, even they were unable to safely navigate the muddy channel. Thanks to local lobbying, the Army Corps returned that year for a $9.7 million dredging of the river, with the understanding that it would be their last.

By that time, most of the industrial sites on the riverfront that once neighbored Aanunsen’s oyster shell yard had been converted to infill housing, shopping malls, and office space, reflecting Petaluma’s transformation from an agricultural shipping hub to a suburban community.

In 2022, Lind Marine announced plans to replace its historic shell plant with an infill housing development.

It will be named Oyster Cove.

John Sheehy is a native Petaluman. He is the author of “On a River Winding Home: Stories and Visions of the Petaluma River Watershed,” and writes about local history on his blog PetalumaHistorian.com.