How to Research with Sanborn Maps, Fire Maps, and Survey Maps

By Randy Salars

Sanborn maps provide building-by-building detail of historical towns and cities — construction materials, number of stories, business names, and lot layouts. They are among the most underused and most powerful research tools available.


What Are Sanborn Maps?

The Sanborn Map Company produced detailed fire insurance maps for over 12,000 American towns and cities from 1867 to 2017. These maps show individual buildings, streets, lot numbers, building materials, and occupancies.

What Sanborn Maps Show:

  • • Building footprints with construction materials (brick, wood, iron)
  • • Number of stories and roof type
  • • Business names and occupancies
  • • Street names and lot numbers
  • • Fire hydrant locations and water sources
  • • Railroad sidings and industrial infrastructure

Where to Find Them

  • • Library of Congress — Largest free collection of digitized Sanborn maps (loc.gov/collections/sanborn-maps)
  • • ProQuest Digital Sanborn Maps — Complete digital collection (subscription, available through many libraries)
  • • State libraries and university libraries — Many hold physical copies and microfilm
  • • Local historical societies — May hold unique editions not digitized elsewhere

Other Survey Maps for Research

USGS Topographic Maps

Multiple editions spanning 100+ years. Compare editions to see how terrain, roads, and development changed.

GLO Survey Plats

Original government land surveys with section lines, natural features, and early settler notations.

Railroad Survey Maps

Detailed surveys of railroad right-of-way, including adjacent properties and terrain.

County Atlases

Published in the 1870s–1900s, these show property owners by name on detailed maps. Gold mines for genealogists and treasure researchers.


Master Map-Based Research

The Treasure Hunter's Research Guide includes detailed map interpretation techniques and overlay methodology.

Get the Research Guide →

Related Pages

Treasure Research Intelligence

Map research techniques, Sanborn guides, and survey analysis.

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