USGS
Triangulation Station
"SAMMIS"

1893

Jerry Penry
April 16, 2010

Triangulation station "Sammis" is the location of one of the original U. S. Geological Survey points established in 1893 in the Black Hills region. The early description for this marker stated that it was a chiseled "+" and lettered U.S.G.S. on a large stone. At some point in time, possibly 1925, a brass disk was cemented to the top of the stone. In 1950 the U. S. Coast & Geodetic Survey (USC&GS) used the monument in their own triangulation network and established two reference marks. The NGS (USC&GS) datasheet for this marker, PU2305, states that this point was monumented in 1950. The style of the brass disk in the stone by USGS is much earlier than 1950. It is my belief that the brass disk was placed ca. 1925 by USGS when they were doing additional triangulation in the Black Hills area.

The original 1893 stone marker and later brass disk that was cemented into the top marking the location of triangulation station "Sammis".

Location of station "Sammis" southwest of Rapid City as shown on the U. S. Geological Survey's 7.5-minute quadrangle sheet.

Aerial image of the location of station "Sammis". Looking northeasterly.

View of the stone marker. Skyline Drive is just beyond the marker and the photo is looking to the northeast over Rapid City, South Dakota.

Jerry Penry with the original 1893 triangulation station established by USGS.

Closeup view of the bottom letters "G" and "S" that were chiseled into the stone in 1893 when the point was first established.

Closeup view of the U.S. Geolgical Survey brass disk that was cemented into the top of the stone.

Reference Marker No. 1 which was placed by USC&GS in 1950.

Closeup view of Reference Marker No. 1 with the damaged brass disk.

Reference Marker No. 2 which was placed by USC&GS in 1950.

Closeup view of Reference Marker No. 2.

Back to USGS Black Hills Triangulation

© Jerry Penry 2010