USGS
Triangulation Station
"DUNNING"

1893 & 1925

Jerry Penry
May 30, 2010

The original USGS triangulation station designated as "Dunning" that was established on a hill east of Rapid City, South Dakota, in 1893, was described as being a chiseled "+" with the chiseled letters "U.S.G.S." on a boulder. When USC&GS arrived at the same hill in 1925, that agency established their own triangulation station monument consisting of a brass disk in a concrete pad. Reference Mark No. 1 was established at that same time which was also a brass disk in a concrete pad. The USC&GS surveyors noted the presence of the USGS boulder and designated it as being Reference Mark No. 2 to their own triangulation station. This boulder was described as having a cross on top and was approximately 1.5 meters east of the brass disk in concrete.

In 1950, USC&GS recovered their monument and established an Azimuth Mark. In 1951, USC&GS recovered the USGS monument and noted that the letters "U S" were engraved on the southeast edge of the boulder. The distance between the USGS boulder and the USC&GS brass disk in concrete was measured to be 5.14'. In 1961, USC&GS established Reference Mark No. 3 at the triangulation site. During this recovery, the USC&GS surveyors noted that Reference Mark No. 2 was a rock about 10" in diameter with the letters "U.S." and the chiseled cross on top.

The site of the triangulation station is on the same hill as a Federal Aviation Administration facility and access is prohibited without first obtaining proper clearance to be upon the property. The hill is located approximately halfway between the Rapid City Municipal Airport and Ellsworth Air Force Base.

Upon examination of the site, there was one well-set stone and several loose stones near the 1925 USC&GS brass disk in concrete. The well-set stone appeared to be limestone and was flaking away. It fit the location of the original USGS stone, but no chiseled cross or letters could be discerned upon it.

Looking southeast at the hill where station "Dunning" is located.

Looking north from the hill toward Ellsworth Air Force Base.

The brass disk in concrete placed by USC&GS in 1925. The stone to the right is a random field stone of no significance.

Close-up view of the 1925 USC&GS brass disk.

View of the 1925 USC&GS brass disk in concrete (far left) and the 1893 USGS stone (far right). The other stones are random field stones. The view is looking north.

Looking west over the 1893 USGS stone and the 1925 USC&GS brass disk.

The southeast side of the USGS stone which is reported to have the chiseled letters upon it. (Reference Mark No. 2).

The northwest face of the USGS stone. (Reference Mark No. 2).

Reference Mark No. 1.

Close-up of Reference Mark No. 1.

Reference Mark No. 3 that was established in 1961.

Close-up of Reference Mark No. 3.

Back to USGS Black Hills Triangulation

© Jerry Penry 2010