In the early 1920s, a dispute arose between Maricopa and Yavapai Counties regarding the location of their common border as it had been surveyed. The counties agreed to resolve the dispute by contracting with the US Coast & Geodetic Survey to resurvey the boundary as an independent third party, and in 1924 the USC&GS laid out and surveyed a triangulation network along the boundary line. When the network was completed, they were able to set monuments precisely on the boundary using offsets from the positions that had been determined for the stations in the network.
The normal procedure used in naming triangulation stations was to derive a name from a prominent local feature. The survey crew in this instance varied from that procedure and chose to name the station on this nameless sub-peak after one of their co-workers, Signalman Jasper S. Bilby, who in 1924 had completed 40 years of service in the C&GS.
Signalman Bilby with light reconnaissance buggy, Minnesota 1903. Courtesy NOAA Archives
Bilby was not a part of the crew which performed this boundary survey, but he had surveyed in Arizona previously. He performed reconnaissance duties in 1908 and signalman duties here in 1910-1911 as the Texas-California Arc of Primary Triangulation was surveyed across Arizona. Our mountainous terrain allows for long sight lines and limited the need for perches such as the one below:
Signalman Bilby on reconnaissance, Minnesota 1903. The top of the stand is 104' above the ground. Courtesy NOAA Archives
Signalman Bilby became most well-known for designing an observation tower which came to bear his name. The Bilby Tower was portable and reusable and greatly reduced the costs of surveying across flat terrain, where previously semi-permanent wooden towers had been constructed. It consisted of two independent towers erected in such a way that a surveying instrument placed on an inner tower would not be disturbed by the movements of the surveyor, who stood on an outer tower. These towers became a standard part of the USC&GS surveying arsenal, and remained in use until 1984. An informative cover story with more biographical information about Signalman Bilby's career as well as more details regarding the tower was recently published by American Surveyor Magazine. A 2.1 MB PDF file of the article is available for download here.
Bilby Tower schematic drawing. Courtesy NOAA Archives
Expect to spend the better part of a day reaching this location. Several different approaches are possible, any of which will likely require an off road vehicle (hence the 5 star terrain rating) to reach a reasonable launch spot for the hike. In order to preserve the challenge for future seekers, please refrain from including in your log any specifics regarding your route.
One point of interest that you may have reason to pass by is a cairn marking a point on the boundary as originally surveyed, which can be found at the included waypoint below. The error of the original survey at this location can be seen by comparing this point with the location of the true boundary line, which passes very close to ET0925 SUMMIT across the way to the north. If you look up to SUMMIT, you may be able to see the sighting mast from the 1924 survey, which remains upright and in place over the station.
Many thanks to AZcachemeister for accompanying me on the trek to place this cache and for providing the necessary transportation!
An unactivated geocoin with an appropriate theme awaits the first finder. Congratulations to smgsmg for claiming it!