An insurance
map at
street level.

The city becomes a set of questions.

A railway map helps us follow a connection. A pictorial map can make a landmark loom over its neighbors. This map brings our attention down to individual walls. A small structure behind a larger building, a change in construction, or a note about a water supply can become worth recording.

Sanborn maps were made to help fire insurance agents assess property hazards. Their outlines, colors and symbols record construction and other details relevant to that work. The purpose helps explain why an ordinary building may receive more technical attention here than a monument does on another kind of map. Inspect source

Our specimen is Phoenix in June 1893. The Library of Congress catalogs an edition of fifteen sheets; its title page names the Sanborn-Perris Map Co. We will read sheet 3 and use the original key on sheet 1. The date belongs to the publication. It does not tell us that every mark was observed on the same day. Inspect source

A building has more than an outline.

Begin with the ice factory. The building drawing and the adjacent writing cooperate. One gives shape and position; the other describes aspects of operation. The factory’s name is only the beginning of the record. Fuel, staffing and water appear in the same small space.

Read those statements as the map’s account. A note that water came from a well and the city is evidence of what this sheet records, rather than an independent inspection of the system. The map provides a precise starting point for another question: which records could help us check how that supply worked?

Now choose Houses. Follow a pink area into an attached yellow portion. Instead of treating each footprint as a single colored object, look for the joins. The map can distinguish parts within one structure. The surrounding letters, roof marks and numbers then ask for another layer of reading.

Finally, look at the hotel and stable. The large crossed rectangle is a useful test: can you find the corresponding sign in the key? A repeated mark becomes readable when it has a declared meaning. Without that key, a confident guess may still be wrong.

Let the old sheet explain its own language.

In this edition, yellow indicates frame construction and red indicates brick. Brown indicates adobe. Those distinctions come from the key printed with the Phoenix maps. The scans preserve variation in the paper and ink, so a color name can be more dependable than an exact screen shade.

III / LET THIS EDITION EXPLAIN ITSELFORIGINAL KEY

THREE MATERIAL READINGS

Frame

The key calls yellow buildings frame. Begin with the small yellow footprints.

Brick

The key calls this red; the surviving scan often appears pink. Read the name with the color.

Adobe

Brown means adobe in this edition. This key also distinguishes stone and iron.

The swatches are reading aids. The scan preserves the original marks and color variation.

Sanborn-Perris · Library of CongressSource & rights +

Phoenix, June 1893 — original map key. Library of Congress, Geography and Map Division, Sanborn Maps Collection.

The Library of Congress identifies its online Sanborn Maps Collection as public domain and free to use and reuse. Source credit: Library of Congress, Geography and Map Division, Sanborn Maps Collection.

Inspect / copy citationOpen source record ↗Open full-resolution scan ↗

The key is also a compact grammar of lines and marks. It distinguishes walls above the roof, openings, windows, roof types and other building features. A color alone does not carry the whole description. Nor does the amount of colored area, by itself, provide an insurance price or a simple ranking of danger.

The Library of Congress cautions that Sanborn symbolization evolved. A convenient general legend can help orient a reader, but the legend issued with an edition is the closer guide to its conventions. Here the blue label means stone. Carrying a different edition’s meaning into this sheet would change the reading. Inspect source

Color also deserves a second check when you move away from the buildings. On the atlas index, broad colored areas direct the reader to numbered sheets. A yellow patch there is a coverage cue. It does not mean that every building within the patch is made of wood.

A close reading needs an outside.

IV / A MAP OF THE MAPSSHEET 1

Find the sheet before the street.

On this graphic index, the large 3 sends you to the sheet used in our close reading. Its colored areas organize the atlas.

These colors do a different job from the colors inside building footprints. The same visual language can change meaning within one publication.

Explore the original index ↗

Unfold the full title and index sheet

Sanborn-Perris · Library of CongressSource & rights +

Phoenix, June 1893 — title and sheet index. Library of Congress, Geography and Map Division, Sanborn Maps Collection.

The Library of Congress identifies its online Sanborn Maps Collection as public domain and free to use and reuse. Source credit: Library of Congress, Geography and Map Division, Sanborn Maps Collection.

Inspect / copy citationOpen source record ↗Open full-resolution scan ↗

The close-up makes small writing accessible, but it removes neighbors. Return to Whole sheet and notice what reappears: the compass, adjacent blocks, street names, continuation numbers and scale. North points toward the left. Keeping that orientation visible helps us resist treating the top of every map as north.

The title gives a scale of fifty feet to an inch for the original maps. A scan displayed on a phone or enlarged on a monitor changes physical size. The printed scale remains part of the source, but an inch on your screen is not automatically an inch on the historical sheet.

There is another outside too. A technically detailed building record does not tell us everything about the people inside it. The selected details do not name each resident, describe a household’s routines, or tell us how a place felt. Those questions invite other evidence: directories, photographs, letters and additional maps.

We can now connect this ordinary block to the larger atlas. Landmarks show how prominence is drawn; insurance maps show how a practical purpose changes the detail worth preserving. Both ask us to read the choices between the world and its representation.