The ruin of America’s first high explosives factory is in Glen Canyon, an urban park in San Francisco. The Giant Powder Works exploded in November 1869 after only eighteen months of producing the new explosive: dynamite. The blast was shockingly powerful—far more powerful than the black powder familiar to California gold mining. A local newspaperman described a factory “torn to hundreds of pieces . . . the entire works are a wreck, the only things left being the planks of the buildings scattered about the place.”

I asked Evelyn Rose, PharmD, clinical pharmacist, local historian, and founder of the Glen Park Neighborhoods History Project, to show me what remained of the wreck. Evelyn has made it her life’s work to document the history of her neighborhood. I asked for Evelyn’s help to imagine the powder works as they might have been.

As if proving the power of dynamite, there was little left for Evelyn to show me. We met at the park Friday before work and, as the sun peeled off the fog of early morning, we examined remnants from the explosion. Evelyn had curated a few of the “hundreds of pieces” in a shadow box with little printed labels by each item.

“This is a piece of redwood that was probably used in the original building construction. You can see the original dovetail . . .”

There’s another fragment of curved wood from a vessel. Lots of molten glass. Scorched rocks. Molten lead chunks. No piece larger than my hand. It slowly dawned on me that she found these items by herself.

“Did you dig these up?”

“Oh, no, the gophers dug this up! I was just lucky.”

I was impressed by her attention to the land. No archaeologist has made a study of the site. A recent remodel of the recreation center plowed through any remaining structures in the soil. Evidence of explosions are fragile; they are evidence of the absence of a thing. In militarized ecologies—where destruction layers upon destruction and debris is repurposed into everyday life—our ruins are also destroyed. Now, the playground sits atop the flattened factory.

I found it difficult to hold the place in my mind: to visualize the factory and its destruction layered together. It was a thaumatrope—two images that I must spin until they combine. This feeling of two-at-once is a common feature of explosivity and militarized landscapes.

Evelyn handed me a clipboard with her recreated map of the manufactory superimposed over satellite imagery. I held her map out in front of me, trying to place the destroyed buildings into the park scene: the manufactory would have been parallel to the tennis courts, and roughly double in size. Two tanks drank up water from the creek for cooling the nitroglycerin. Next to the recreation center there stood the pack house and drying house for the sticks of dynamite. Where the baseball diamond is today, the chemist lived in his cottage. Beyond that, the Chinese workers lived on-site in a small building labelled “shanty.” Two workers died and seven others were seriously injured in the explosion that destroyed the factory.

I looked up and saw eucalyptus dense around the baseball field and recreation center. The trees were planted in the 1880s and early 1910s as a source of timber. The canyon walls served as a natural buffer against explosions. Trees still clustered at the entrance of the canyon. Beyond the eucalypts, the canyon sloped up into golden chaparral blemished by large lichen-covered rocks.

“The whole area was just dairy farms and wilderness at the time the factory was here.” Evelyn pointed up slope to the chaparral beyond the trees. “There would have been very few trees, then; the forest came later, planted. That’s what this whole area was like in the old photographs.”

The two of us were engaged in forensic mapping (or reclamation, or maybe demilitarization) to recover the blast site beneath the baseball field. I was not sure what this practice meant to Evelyn, but to me it was an ethical practice of re-storying history and reclaiming the ground of my childhood. I grew up in the San Francisco Bay Area without ever knowing its history of explosives manufacturing.

There are no photographs of the factory proper. Evelyn sent me an old black-and-white photo that showed a nearby part of the canyon as it looked in 1891. The hillsides ruffled with grasses and flowers in an irregular pattern that looked very foreign from the parkland of today. The long stalks of something like wheat bent in clumps, blurred, to show the power of the wind. There were pale flowers, perhaps irises. There were no trees. The hills were scarred by roads and fences and rock outcroppings (those I recognized) and the small black shapes of people on the roads, looking like thin, leafless trees rooted because there was no clear reason why they were there or where they were going. Every person, fence, and thing looked as if it had been placed there, told to stay put, and then abandoned. There was nothing to do: the only building had no visible doors and an empty smokestack. The creek through the canyon was dammed. It was a scene of morose inactivity, a purgatory hard to imagine. The hills disappeared into billows of white, clouds textured in waves, and it looked as if the sea had risen to devour them.

These field visits, maps, and photographs are how I hold the thaumatrope in my mind. Our forensic imaginary—to imagine things that destroy themselves—to look over the edge of violence while still holding ourselves to this life.