Land Surveying Incorporated

209 N. Works Ave.
Gillette, WY 82716

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Initial Point of the Black Hills Principal Meridian


The initial point for land surveys in the Black Hills region and the western portions of South Dakota lies at the intersection of the Black Hills Base Line and the Black Hills Meridian. The Black Hills Meridian represents the western boundary of South Dakota, while the Base Line runs perpendicular to it. Where these two lines intersect is known as the “Initial Point” of land surveys in the Black Hills region.

On September 1, 2019, Stacy, Cevin, and Larissa set out to visit the U.S Forest Reserve Black Hills Boundary Post No. 140, the initial point of the Black Hills Meridian.  Our goal was to discover the survey monument set by William H. Thorn, a surveyor that worked with the U.S. Geological Survey back in 1899. 

We set out planning for a short adventure, only to be quickly overwhelmed by the number of dead trees, some standing and some partially fallen. It turns out the recent Black Hills National Forest pine beetle epidemic that killed millions of trees in the region had made our adventure much more difficult and dangerous than we had expected. Very soon into the hike we began to ration our bottles of water.  What had looked like a simple hike on our smartphone maps was going to require significantly more effort than previously thought because of the fallen trees. 

After a significant effort and plenty of sweat, the monument ended up being more than any of us expected – a 4-foot long iron post partially buried in the ground surrounded with a 4-foot diameter collar of local stone projecting 2-1/2 feet or more above the ground.  The large iron pipe was 3-1/2 inches in diameter, having a large 4-inch cast brass cap riveted to the post. A very substantial monument even in modern times, you can only imagine the work it must have taken to establish this monument in 1899.  

Img 1583 E1570721087137 1The rock pile and monument at the initial point of the Black Hills Meridian.


As we sat at the Black Hills Meridian point, we reflected on all the previous surveyors and the history that had taken place right there at that exact spot over the last century and a half.  It is impressive to think of the surveyors placing this monument in 1899; however, this point was originally established 22 years prior to that when the Civil Appropriations Act of March 3, 1877 created the funding for the Wyoming-Dakota territorial boundary to be surveyed and monumented.  On April 6, 1877 the Commissioner of the General Land Office (James A. Williamson) contracted with Rollin J. Reeves, Surveyor and Astronomer, to survey approximately 138 miles of the territorial line between Wyoming and Dakota Territory.  More specifically, the state line was drawn between the 43rd parallel and the 45th parallels of latitude along the 27th degree of longitude west of Washington D.C.  Reeves began his survey at the northwest corner of Nebraska, a monument that had been established on September 6, 1869 by Oliver N. Chaffee after surveying along the 43rd parallel.  Reeves and his crew took astronomic observations using Polaris to determine the starting azimuth surveying north.  We can only imagine the work and calculations that had to go into the Polaris observation, as the survey work had to take place on clear, dark nights in rough terrain. Furthermore, the work was done under constant threat of Indian attack. 

Modern day land surveyors, such as ourselves, are accustomed to working with the conveniences of modern technology, smartphones, and GPS technology. State Plane and geographical coordinates derived from equipment of modern times allow us to forget how difficult it once was. We enjoy visiting significant and historical landmarks such as this one, as it gives us a chance to reflect on the past, present, and future of land surveying.


Author Info:

Cevin Bio

Cevin Imus has been a Professional Land Surveyor with Land Surveying Incorporated since 2000, and owner of the company since 2007.  He has 30 years of professional experience as a land surveyor working throughout Wyoming, Nebraska, and Montana.  Cevin supervises the daily operations of all employees at Land Surveying Incorporated, schedules surveys, as well as business, project, and client management.


3 Responses

  1. Once again impressed with dedication to his profession, Cevin is shown to be an outstanding member of the Surveying profession.

  2. All of the astronomical observations for Reeve’s 1877 survey of the Wyoming-Dakota boundary were made by H. P. Tuttle, (of the Newton-Jenney survey, who was the former famous comet discoverer at Harvard) using a Blunt theodolite for azimuths and Stackpole lunar sextant for time and latitude. Starting at the Initial Point on June 6, 1877, Tuttle determined the error of his sidereal chronometer by double altitudes of Altair. Using logarithms he found the azimuth of Polaris at greatest eastern elongation (sin az = sin (90 – declination) sec latitude. He computed the time of greatest elongation, and having left the transit on the line, about 20 minutes before elongation, he set Polaris on the horizontal and vertical wires. He tracked it till it stopped moving to the right, where it would stay at greatest elongation for about 17 minutes. The transit could then be turned off his calculated Polaris elongation east, to the meridian. The survey party was plagued by poor weather and harsh conditions, and on 21 July 1877, when about 5 miles from camp, their small Army escort was driven off, their wagons stripped of duplicate records, instruments and supplies, forcing a retreat to the Black Hills with only six miles to the 45th parallel to go. Returning to the line on 30 July, Tuttle faced rainy weather till 1 am. Hostile Indian fires were seen “in all directions, and so great was the alarm with our small escort that a moment’s delay after the observations were made was deemed dangerous, if not fatal, to the whole party.” Double altitudes of Polaris had to be “rapidly made, and the mercury in the artificial horizon was seriously disturbed by the walking in the immediate vicinity fo the observation spot, of the cavalry horses, which no appeal of Mr. Reeves or myself could compel the officers to remove to a proper distance.”

    1. Thank you for the added detail! We can only imagine the amount of detail and effort it took to produce these measurements.

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