Interpreting Dates

Publication Dates

For the first half century of fire insurance mapping, the dating of editions is generally straightforward. For small-town maps issued in loose-leaf format, the first page and generally each subsequent page carried the month and year of publication quite prominently in an upper corner of the map. The year of publication was usually repeated as part of the copyright notice that appeared as part of or adjacent to the title.

The dating of multi-volume editions of large-city maps is somewhat more complicated. The date on the first volume may be valid only for that particular volume, as the subsequent volumes may have been issued over a period of years. In several cases, a single volume within a multi-volume set was revised and reissued with a new date even before the whole edition was completed. In Fire Insurance Maps in the Library of Congress, therefore, date ranges are given for the coverage of multi-volume editions.

Corrected Editions

Beginning around 1920, the dating of an edition becomes rather complicated. In response to various economic factors around that time, the Sanborn Map Company began updating maps for its customers by issuing paste-on correction slips. These were generally applied by a company employee, who then annotated a chart, usually entitled "Correction Record," attached to the title page, recording the dates on which corrections had been applied. Such correction slips were intended to keep the map coverages current. Over the years, however, more and more correction slips were added, and it is impossible to determine which correction slips were applied in which years. For many cities, as many as fifty or sixty series of correction slips were applied over the course of thirty or forty years. In Fire Insurance Maps in the Library of Congress, the dates for such editions are the date of the original printed edition of the map and the latest date for which corrections were applied.

The latest date, however, is not always found in the "Correction Record." In many cases, additions to indexes pasted into an atlas are later than the last correction slip annotation indicates. In Fire Insurance Maps in the Library of Congress, the latest date of an edition or volume reflects the latest date found on any material pasted into that volume or edition.

The vast majority of examples of paste-on correction sheets in the collections of the Library of Congress come from the maps produced by the Sanborn Map Company from the late 1920s. This technique, however, appeared very early in the history of fire insurance mapping. When significant changes took place in a city, it was important to update the fire insurance plans. In some cases, the amount of change did not warrant mapping the entire city again. In other cases, it may have been prudent to update certain key changes even before the whole city could be re-mapped. To accomplish this, fire insurance map producers printed a correction sheet that was pasted over the incorrect information. Charles Rascher, for example, in his 1891 atlas of Chicago, includes seven different updates printed on a single sheet. Where a map producer had inventory in stock, the corrections could be applied before the volume was sold. At least some companies offered the service of sending employees to customers' offices, where the correction sheets could be applied on site.

How to interpret:

• Block Numbers
• Reports on Fire Protection
• Congested Districts
• Scales
• Sheet Numbers
• Indexes (Graphic, Special, Street)
• Water Systems