How the British Mapped the Province of New York, 1720-1775

David Allen’s presentation on How the British Mapped the Province of New York, 1720-1775 provided us with a peek at some of his current research into the history of New York maps. He begins in 1720 with Cadwallader Colden, who was Surveyor General of NY from 1720-1725. Between his service and that of his 2 sons, the Coldens were Surveyors General from 1720-1775. Colden was probably the 1^st to realize that the Hudson, with portages to lakes Ontario and Erie, could allow the British to take control of the fur trade from the French. David then introduced the two main types of mapping of particular importance to the British in early New York: military and property. Later in his presentation he spoke about the influence of John Campbell, the Earl of Loudoun on the accuracy of maps. Campbell was sent by the British as General Braddock’s replacement. Campbell knew the army needed better maps and so had the British Army make maps.

David used several old maps to demonstrate techniques he is using to compare and analyze maps. He uses Adobe Photoshop to simplify coloring (e.g., reduce to black and white, or blue and white) and then to overlay maps for easy comparison. Applying this technique enabled him to show several versions of the way the Hudson and Mohawk rivers were mapped over time, the influences prior maps had on later maps, etc.

Another analysis tool David uses is Map Analyst, which is a free program (available online: http://mapanalyst.cartography.ch). Map Analyst allows you to compare old maps to modern maps. With it you can match locations on modern maps with the old maps and create displacement vectors and circles of uncertainty. With maps analyzed using Map Analyst and marked with circles of uncertainty, David illustrated the increasing degree of accuracy on maps of the Hudson and Mohawk Rivers. He also provided the historical background to explain the differences among the maps.

David’s presentation, particularly the use of new technology tools to analyze old maps, was a great finish to a day filled with technical information. The challenges David faces in finding the information about who made which maps, based on what previous maps, using which method and why actually drives home the importance of issues we discussed earlier in the day such as collecting and preserving, creating metadata, and managing digital rights and access!