What Are Sanborn Fire Insurance Maps?

Between 1867 and 1970, the Sanborn Map Company produced extraordinarily detailed maps of more than 12,000 American cities and towns. Originally created for fire insurance underwriters, these maps documented every building in a city — its size, shape, construction material, number of stories, and use. Today, they are among the most valuable primary sources for understanding the built environment of American cities during a transformative century.

The Sanborn Map Company

Daniel Alfred Sanborn founded the company in 1867 in New York City. What began as a small operation producing maps for insurance companies grew into the largest map-publishing firm in the United States. At its peak, Sanborn employed hundreds of surveyors who fanned out across the country, meticulously documenting every structure in cities large and small.

The company's maps were used by fire insurance underwriters to assess risk. An underwriter could look at a Sanborn map and instantly determine whether a building was made of brick or wood, how close it was to neighboring structures, whether it had fire walls, and what was stored inside. This information was critical for setting insurance premiums in an era when urban fires could — and regularly did — destroy entire city blocks.

What Makes These Maps Special

Sanborn maps stand apart from other historical maps for their extraordinary level of detail. Each map shows individual buildings drawn to scale, with color coding indicating construction materials: pink for brick, yellow for wood frame, blue for stone, and green for iron or steel. Building footprints include notations about the number of stories, basement presence, roof type, and specific uses like “dry goods,” “saloon,” or “livery stable.”

But what draws many people to Sanborn maps today has nothing to do with insurance underwriting. The title pages of these maps — especially those produced between 1880 and 1920 — feature stunning examples of Victorian-era typography and graphic design. Each cover was hand-lettered with elaborate decorative type, ornamental borders, and intricate cartographic details unique to the city it represented.

Bridgeport, Connecticut (1913)Hartford, Connecticut (1922)New Haven, Connecticut (1901)

Why Sanborn Maps Matter Today

Long after their original purpose became obsolete, Sanborn maps have found new life as indispensable tools for a wide range of disciplines:

• Urban historians use them to trace how cities grew, changed, and sometimes shrank over decades of rapid development.
• Environmental professionals rely on Sanborn maps to identify former industrial sites, gas stations, dry cleaners, and other properties that may have contaminated soil or groundwater — a process central to environmental site assessments.
• Genealogists and family historians use these maps to locate ancestral homes, understand the neighborhoods their families lived in, and add physical context to family stories.
• Architects and preservationists consult them when restoring historic buildings, since the maps often document original building configurations long since altered.
• Designers and artists are drawn to the exquisite hand-lettered typography of the title pages, which represent a high point in American graphic design.

The Collection

The Library of Congress holds the largest collection of Sanborn maps, with approximately 700,000 individual map sheets covering cities across all 50 states. Many university libraries and state archives also maintain significant collections.

This archive focuses specifically on the title pages — the ornate covers that introduced each volume. We've digitized and preserved over 3,500 of these title pages, making them freely available for personal use and offering selected maps as museum-quality framed prints.