JOHN SNOW CHOLERA MAP MODEL

John Snow's Cholera Map, 1854

In the summer of 1854, a cholera outbreak tore through the Soho district of London. Within days, the outbreak — centred on Broad Street and Golden Square — had killed 616 people. The physician John Snow, already sceptical of the prevailing theory that disease travelled through bad air, set about tracing the deaths street by street. Using bars to mark each death's location on a map of the neighbourhood, he was able to show that the cases clustered around a single public water pump on Broad Street — and that contaminated water, not miasma, was the cause.

Snow's study became a founding moment of modern epidemiology, and its consequences were immediate: it changed the design of London's water and waste systems, and set a new standard for public health investigation worldwide. The map he commissioned — published in the second edition of his essay On the Mode of Communication of Cholera in 1855 — has become one of the most reproduced documents in the history of science. It is both a piece of rigorous data analysis and something quietly beautiful: a portrait of a neighbourhood rendered as evidence.

Photograph from Wellcome Images, licensed under CC BY 4.0 via Wikimedia Commons.

The Brief

In 2021, the Cabinet Office commissioned Chisel & Mouse to create a data-led wall piece for display in their offices. The subject was to be John Snow's cholera map — a fitting choice for a government building, given the map's enduring relevance to public health policy and data-driven decision-making.

The brief asked for something that felt substantial and considered rather than decorative. It needed to work as a piece on the wall — something you could stand in front of and read — whilst being unmistakably a made object rather than a print.

The Making

After discussion back and forth, we settled on a layered construction that mirrors the map's own logic: information revealed through depth, with each layer doing a different job.

Render of proposed map model.

The model is built up from three layers:

The base layer is white wood — the ground of the piece, giving it weight and presence.

The dark layer sits above it, raised and floating: a metal-etched street network coloured dark, with the cholera death instances marked into it. This is the data layer — the raw record of where people died.

The light layer sits directly on the dark layer, and is where the reading happens. Also metal-etched, it carries the same street network but at a fractionally smaller scale, so a sliver of the dark layer bleeds through at every edge — giving each street a subtle border and a sense of depth. The cholera instances are absent from this layer, so they show through from below. Street names are cut out of the metal, allowing the dark layer beneath to read as type. The water network and the position of the Broad Street pump are also cut through — the pump emerging from the piece as a point of negative space, the detail you notice first once you know what you're looking at.

The whole piece is housed in a wooden frame, finished to approximately 70 × 70 cm.

The result is a map you can read on two levels: as a historical document, and as a study in how data becomes visible. The layering replicates something of what Snow himself was doing — placing information over information until a pattern emerges.

Close up on layers showing streets and deaths.

The Delivery

The piece was completed and delivered to the Cabinet Office in 2021. We have since lost touch with the contact who placed the commission, so we don't know exactly where in the building it now hangs — or whether it's still there. If you happen to work in the Cabinet Office and walk past it, do let us know.

Finished map model.