How do we determine the publication date of antique maps?

Some customers like to see a date printed on a map, and we’re often asked how we know when a particular map was published if that is not the case. We’re always happy to provide a certificate of authenticity for any maps purchased, detailing the provenance of the map and our opinion of its publication date, and to let you know how we dated the map or print.

While older and individually published maps frequently do have a date printed on them, many 19th century and later atlases and books do not state the publication date on each individual map therein. Even where a date is printed on the map, this may be the date or year when the plate was originally engraved – it does not preclude the map having actually been printed later than that, if the publisher did not update the date stated in the plate or block at the time of printing a later edition.

If a map has been extracted directly from an atlas, dating is usually straightforward as the publication date of the atlas is almost invariably printed on the title page of the book (although publication dates of subsequent editions or impressions were occasionally not altered). If we are selling a map that we have purchased as part of a complete atlas, we usually retain the title page, and can produce a digital copy upon request. However, if we are selling an individual map that we have purchased as such, we may need to do a little research and make other checks to verify or estimate the publication date. There are several helpful indicators we can use.

The plates or blocks from which maps were made deteriorated progressively with use; initial impressions made using a particular plate are usually strong, crisp and clear, indicating an early edition, while a weaker impression lacking some fine detail might indicate a later print. 

Then as now, map makers needed to keep their maps up to date with events and new discoveries: changing geographical features such as railways, national borders, or revisions to coastlines reflecting recent surveys often provide important dating clues. 

Plates sometimes stayed in use for decades, and often changed hands between one firm of cartographic publisher and another mapmaker – publishers were usually keen to take credit for their work, and the name of the publisher was usually printed on the map, which can often conclusively narrow the range of possible publication dates. Printed text, and the content or positioning of vignettes or cartouches often changed with subsequent editions of a map.  

Finally, the quality or thickness of paper used may well have changed between publication of different editions or impressions, and old paper used in map making often contained a watermark which can provide an important clue as to the provenance of the map. Such changes are usually catalogued in the many thoroughly-researched cartographic reference books available to map dealers which detail the various progressive states of each important map. 

For example, Camden's Britannia, originally published in Latin in 1586 by William Camden, was later republished in four English editions of the atlas translated by Gibson were published in 1695, 1722, 1753 and 1772, each accompanied by the highly regarded maps of Robert Morden. If acquired as separate sheets, the maps can be dated by reference to the size and thickness (the first edition was printed on smaller sheets with narrower margins, and thinner more brittle paper), and by holding the paper up to the light to see the watermarks and other distinguishing features, which differed from one edition to another.

Certain maps may be closely dated by reference to the content of the map. Several editions of Bacon's Large Scale Atlases of London, published between the late 19th century and approximately 1930, did not contain a date on the title page, however this during London's period of rapid development and growth, and it is always possible to date these atlases accurately by comparison with other maps, or the known date of new developments and buildings. New stations were frequently added to the London Underground network during this period, and their names changed; their inclusion or exclusion can usually help to pinpoint the date of publication of the map very closely.

In general terms, printing methods used varied and evolved over time, and each printing method imparted differing physical characteristics onto the page; it is usually possible to estimate a rough publication date from simple observation of the physical characteristics of the map or print. For example, engraved copperplate maps were inked and applied to the page under pressure to create printed maps, leaving a distinctive platemark around the edge of the map. Copper was increasingly replaced by the use of steel for engraving from around the 1820s; steel allowed for finer detail to be imparted onto the plate, and was harder wearing, allowing for more impressions to be made before the plate wore out. It is usually possible to tell a copperplate from a steel impression by reference to the level of detail contained in the image. Engraved plates, printed using a press, often resulted in parts of the sheet. The act of applying pressure to an inked sheet caused the ink to behave in a certain way, in some parts of the sheet the ink might be forced through the paper, causing ink spots on the reverse side, or in attempting to escape the pressure, a characteristic pattern might be seen around the edges of the inked area, awhich can be seen with a magnifying glass. The pressure caused by the printing press on the sheet, particularly in the case of line engravings, also resulted in distinctive elevated ridges on the reverse side of the sheet, which can usually be felt with a finger or thumb. 

Creating engraved prints and maps was a time consuming and expensive endeavour, requiring skilled workmen and artists, first to draw the map or picture, and then to transfer it by engraving onto a sheet of metal or wood. It started to be replaced by much cheaper modern lithographic printing methods from the 1870s, and had substantially ceased to be used as a printing method by around 1910. We can thus be fairly confident that any print or map which displays the physical characteristics of an engraving was printed before this date.