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Mapping Humboldt County
Detailed large-format folding map of Humboldt County, California, with its towns of Eureka, Ferndale, and Arcata, blue printed by the Progressive Map Service.
This 1924 map of Humboldt County, California, compiled and published by Progressive Map Service of Fresno, California, offers a comprehensive depiction of the county’s geographic and administrative features. Presented in a blueprint style, the map uses clear blue linework on a light background to detail settlements, natural features, and infrastructure. A legend in the upper left corner explains the map’s symbols, indicating boundaries for county lines, national forests, and Indian reservations, as well as marking main highways, open roads, trails, railroads, streams, lighthouses, and ranger stations.
The map highlights the rugged coastline of Humboldt County along the Pacific Ocean, extending north to the Del Norte County border and eastward into the national forest lands of the interior. Coastal landmarks such as Big Lagoon, Patrick’s Point, Trinidad Head, and Clam Beach are clearly depicted. Inland, major natural features include the Klamath River and its network of tributaries, surrounded by the vast forested regions that characterize much of the county.
The county’s settlements and transportation network are carefully mapped, with major towns such as Trinidad, Blue Lake, and Orleans prominently labeled. Smaller communities also appear, illustrating the rural character of the region at the time. Main highways, open roads, and trails traverse the county, showing the early road system’s reach in 1924. Railroad lines are also mapped, emphasizing their importance in connecting logging camps and transporting timber—an economic lifeline for the county during this period.
In addition to natural and transportation features, the map highlights Indian reservations and national forest boundaries, reflecting the county’s administrative and cultural landscape. Several ranger stations are marked in the forested regions, while lighthouses dot the coastline, underscoring their role in maritime navigation. These details suggest the map may have served a practical purpose for land management, forestry, or regional planning.
Blueprint & Blue Line maps (Cyanotype Printing)
Blueprint and blue line maps were among the most popular means for the swift printing of maps for which there would be a limited demand. A blueprint or blue line map could be made and/or revised much more quickly than a lithograph, cerograph, or other printing method, and at a much lower cost.
This method of printing was invented in 1842 by John Herschel, a chemist, astronomer, and photographer. A cyanotype process, one starts by drawing on semi-transparent paper, weighted down by a top sheet of paper. The paper would be coated with a photosensitive chemical mixture of potassium ferricyanogen and ferric ammonium citrate. The paper would then be exposed to light, wherein the exposed portions turned blue and the drawn lines, protected from exposure, would remain white.
The cyanotype printing process was an improvement on the expensive and time-consuming method of hand-tracing original documents. The technique was particularly popular with architects; by the 1890s, a blueprint was one-tenth the cost of a hand-traced reproduction. It could also be copied more quickly.
Blueprint and blue line maps began to appear as early as the 1850s and 1860s, but they really began to become the standard for mining and similar limited-purpose maps by the 1880s. The ability to create these maps quickly and at a low cost made them the standard for short-run prints, ideal for mapping mining regions in the West and for similar purposes.
The method still exists today, but in a very limited fashion. In the 1940s, diazo prints (whiteprints or bluelines) became more popular, as they were easier to read and faster to make. The blue lines on a white background of these prints are now what most people call blueprints.
![[Appointment of Ben E.S. Ely as Notary Public for Napa County, California - September 26, 1861]](https://storage.googleapis.com/raremaps/img/small/93309.jpg)
