Semaphore is a multi-faceted public art project funded by the City of San Leandro through a San Leandro Arts Commission Arts & Culture Grant. Its most visible manifestation is a temporary installation of nearly 2,000 vibrant marker flags. Dig a little deeper, and there’s a story about long-distance visual communication, material culture, and the making of meaning. 

This blog details the origin of the word "semaphore" and its many subsequent applications, as well as the industrial origins of the marker flags. Here, too, are notes on the community's engagement with the work, including the "community" of living things and detritus found on the site. Read at random or start from the beginning by scrolling down to the first entry, posted on January 24, 2022.

But first...

Watch Semaphore: The Movie and order a copy of the 20-page monograph from here:

Semaphore: Making Meaning

Semaphore: The Movie

Produced by

Click anywhere to start the video.

That's it!

June 30, 2022

2,000 blue and yellow flags, more or less

Blue out

June 29, 2022

Overcast this morning. All the blue flags have now been removed -- the crescent on the back side of the yellow circle, the escapees on the far side of the fence, all four drops--tear, rain, spermatic, or otherwise.




June 27, 2022

De-installation starts today. One by one, the flags are removed, last in first out.


After (left)

After (right)

A symbol of resilience

June 15, 2022

The artichoke is a member of the thistle family, whose flower is venerated as a symbol of resilience. In Celtic culture, the thistle represents devotion, bravery, determination, and strength. I think of all the ways we -- our planet and all its inhabitants -- are called upon to be strong, determined and brave every day.

Ongoing transformation

May 18, 2022

Semaphore is a process.

The days lengthen.

The great drying out begins.

Someone decides enough already with the weeds.

May 16

May 9

April 25

Aerial view of Semaphore

Photographed by

April 29, 2022


April 19, 2022

The weeds are starting to engulf the flags. This was always going to be a reckoning with Mother Nature. Did I mention I’m not a gardener? Let the weeds have their way, says I.

Early traffic signal

April 12, 2022

As I was digging around to learn more about semaphores – i.e., visual messaging systems – I came across this little bit of history. In 1923, Garret Morgan invented the first semaphore traffic signal, having witnessed an accident at a particularly hazardous intersection in his hometown of Cleveland. The system was hand-cranked by police officers, with rotating arms that read “Stop” on one side and “Go” on the other. When all arms were raised to a vertical position, cars in all directions stopped and it was safe for pedestrians to cross the road. 

This prolific inventor patented his traffic signal in the United States, Britain and Canada, and eventually sold the rights to General Electric for $40,000. It’s also worth noting the Morgan was the first Black man in Cleveland to own a car.

More artifacts unearthed

April 5, 2022

Back in February as I prepared the site for Semaphore, I decided to weed the areas where I would be planting flags. Fragments of pottery, ceramic, and milk glass, as well as rusted nails and assorted other metal fragments, were scattered throughout the soil. They conjure a sense of times past, lives lived. I wonder about the hands that touched them, the purpose they served.

Pottery, ceramic and milk glass fragments

Rusty nails, bolts and hooks

Archeological "dig"

March 29, 2022

This parcel of land on the corner of West Juana (formerly Saunders Street) and Clarke has been appearing on San Leandro maps at least since the town's incorporation 150 years ago. A house first shows up on the parcel in the early 1900's. It was subsequently moved 90° to face Clarke in the 1930's. The corner store was built circa 1938 so that the owner's wife could leave her job at the cannery (where BART now stands) to run a little grocery business. It’s been many different retail businesses since then, but remains a much-loved presence on this downtown corner.   

Pictured below are some of the treasures I dug up while weeding this plot in preparation for planting Semaphore flags.

The land we’re on

March 22, 2022

I want to take a moment to acknowledge that the land where this project is taking place is traditional Ohlone land, home today, and for thousands of years, to indigenous people. Most of us are relative newcomers here, in San Leandro, in the East Bay, in California. For more information about the history and native people of this land, visit It is eye-opening.


The peace symbol

March 15, 2022

Another bit of history about the semaphore code...

Combine semaphore “D” (one arm straight up and one arm straight down) with semaphore “N” (arms down at either side at 45 degree angles). Enclose them in a circle and you have what became the iconic peace symbol of the Cold War.


Designed by Gerald Holtom in 1958 for a British nuclear disarmament protest, the “N” stood for “nuclear”, the “D” for disarmament. It was soon adopted in the United States and around the world to protest war and injustice.


The U.S. Patent and Trademark Office decided in 1970 to keep the symbol in the public domain for all to use.

What we bring

March 8, 2022

Everyone brings a different association to the colors in Semaphore. When I began working on the design late last year, I was reminded of the blue and gold of Cub Scouts. I have three older brothers who were active in scouting as youngsters. I tagged along, the little kid sister. 

Lately, I can’t help but think of the colors of the Ukrainian flag. And that’s true for many visitors to Semaphore as well. I was on-site today, head down, planting more flags, when I heard a voice: “Hello.” Looking up, I saw a middle-aged man, who gestured to the flags and said “Ukraine”. Then, smiling, he pointed to himself, and said, “Ukraine. Kyiv. Kyiv,” and continued on his way.

It is a bittersweet coincidence that I did not anticipate when choosing the colors for Semaphore.

Blue and gold…

March 1, 2022

…And PINK. 

Yellow is bright, cheery, warm. Blue is cool, sophisticated, serious. Pink? Pink’s the wild card, especially hot pink. Packed with energy, it’s not shy.

At 1,100 flags, yellow is dominant. At 900 flags, blue’s no slouch. Pink, on the other hand, tops out at exactly FOUR flags, marking the cardinal points of the compass. Pink cord runs along the ground, connecting each pink flag to the center of the yellow circle. You can see the West flag at the top center of this photograph, peaking out from behind the apricot tree branch. Look at the photograph on March 22 post to see the pink cord running from West to East, and the flag marking East. To it's right, in the shadow of the high fence, is the pink flag marking South.

“Call Before You Dig”

February 22, 2022

What's the origin story of these small but visually striking flags?

In 1976, a petroleum pipeline was breached by a construction crew in Culver City, California, resulting in an explosion and fire that killed nine and destroyed a city block. Color-coded utility marker flags became one element in a variety of measures taken to prevent similar tragedies in the future. 

Each flag color carries a specific message about what lies beneath:

Blue marks drinking water lines. Yellow indicates volatile materials like gas or oil. A pink flag is a temporary survey marking. I like to think of it as connoting possibility.

The flags at hand

February 15, 2022

Take a look around at a nearby construction site. Or maybe your neighbor’s front yard, where they’re digging up a sewer line. Notice some small, colorful flags? 

Decades ago, the construction and public works industries adopted a set of color-coded flags to mark the location of underground utilities and site boundaries. Called utility marker flags – or just marker flags – surveyors and landscapers use them, too. 

While contractors, surveyors and landscapers use them to avoid damage to underground infrastructure, this artist is using them for their vivid colors, flexible strength, and animation.

Language of the ocean

February 8, 2022

While fixed towers made sense on land, they made no sense on ships at sea. Instead, hand-held flags replaced the arms of the semaphore towers for ship-to-ship and ship-to-shore communications beginning in the 19th century. 

Today, flag semaphore is still used for emergencies at sea. Red and yellow flags held in specific positions spell out a message. The most famous is “SOS”, signaling distress.

Curiously, the peace symbol also came out of the semaphore code. And what about the original traffic signal system? More on those another time. 

First a little history

February 2, 2022

Long-distance visual communication has been around since the dawn of human history, from hand signals to smoke signals to torches and lamps.

In 1792, Claude Chappe coined the word “semaphore” for the network of communication towers he built in France. Each tower had pivoting arms that could be arranged to spell out a message in code, visible to the next tower. Thus were military dispatches sent and received during the French Revolution. 

Similar optical communication systems proliferated around the world over the next 50 years. Our own Telegraph Hill in San Francisco is named after the semaphore tower built there in 1849 to signal the arrival of ships into the Bay.

So where do flags fit in?


January 24, 2022

Semaphore. What does it mean? The word has its roots in ancient Greek. Sema means marker, flag, or sign. Phero means to bear or carry. Flag carrier. Sign bearer. So, roughly speaking, a way to convey information or meaning visually, at a distance.

Over the next few months, I’ll be posting here as I plant hundreds of brightly colored marker flags in an urban oasis at the corner of Clarke and West Juana streets in San Leandro, California.

I invite you to click on Contact to ask me questions, leave a comment, or just to express your reaction.

Together, we’ll be making meaning. Let’s get started!

Semaphore is a temporary, site-specific sculpture funded by the City of San Leandro through a San Leandro Arts Commission Arts & Culture Grant.