Hudson and her colleagues have systematically studied European and American cartographers and have discovered that women mapmakers have often been overlooked and their work has been unrecognized. They have succeeded in identifying approximately two hundred pre-twentieth-century mapmakers, most of whom worked in Europe.

Several well-known historical maps and atlases in the Library's collections were produced by women. For example, Mary Biddle's name appears on the 1762 version of the Scull and Heap Map of Philadelphia as its joint editor with Matthew Clarkson. The oldest child of Nicholas Scull and Abigail Heap, Biddle married at age nineteen and gave birth to ten children. She apparently learned her cartographic skills from other members of her distinguished family, and when she and her husband fell upon hard times, she contributed economically to the family unit by editing this well-known map. The map, seen left, was republished a number of times, but this is the only edition that acknowledges Biddle's contribution. Both she and Clarkson are identified on the piece as the map's sellers, another example of the multiple roles women played in the early American map trade.

Although Eliza Colles died in 1799 at the age of twenty-four, she had already engraved maps for her father, Christopher Colles, the publisher of the first American road atlas. Her name appears on plates 1 and 5 in the Geographical Ledger and Systematized Atlas by Christopher Colles of New York.

Women were also map publishers. Esther Lowe of New York published several maps and reissued an encyclopedia while working in New York between 1810 and 1815. Lydia Bailey of Philadelphia was one of the most prolific of the women printers. She printed engraved maps, one of which appeared in 1830 and was used to illustrate a work on internal waterways in the United States. The Farmer family, consisting of the widowed Roxanna, her daughter Esther, and her two sons, took over the family business after the death of her husband in 1859. An example of Roxanna's work is a railroad map issued in 1862.

Ellen Eliza Fitz, an American working in Canada as a governess, in 1875 obtained a patent for an invention to mount globes. Her innovation mounted the globe so as to show the position of the sun and the length of days, nights, and twilight for the entire year. In her Hand-Book of the Terrestrial Globe; or, Guide to Fitz's New Method of Mounting and Operating Globes, designed for the Use of Families, Schools, and Academies she explained how it worked. Two of Fitz's globes, mounted and operated as she describes, are in the Geography and Map Division.

Even though the number of American women working in the map trade before the twentieth century was small, the works that they produced were of noteworthy quality. Little has been written about twentieth-century American women who may have continued this tradition. As Alice Hudson points out, considerably more research needs to be done in all areas where American women participated in mapmaking. Possible topics include the role of marriage and family patterns in the map trade, a reexamination of the navigational role that Sacagawea played as one of the leaders of the Lewis and Clark Expedition, and why so little is known about the work of twentieth-century women who seem to have disappeared from the scene after women contributed so richly in earlier eras. Hudson's own contribution to the field has been to heighten awareness of the scope and extent of women's cartographic activities and accomplishments, as well as collecting detailed information on women cartographers.