Missouri River Commission
Triangulation Station

Recovery & Remonumentation of a
120-Year-Old Survey Marker
Jerry Penry
April 14, 2006

In the 1880's the Missouri River Commission (MORC) established a precise network of triangulation survey monuments along the bluffs of the Missouri River as primary control points to be used for the mapping of that river. The monuments this agency used were well ahead of their time, and were intended to be very permanent. Although they were set in remote areas 120 years ago, there are very few of these triangulation markers still in existence due to curiosity seekers, vandalism, urban growth, and accidental destruction.

The monuments consisted of a lower 18" square limestone block 4" thick with a drill hole in the center. Centered above the drill hole was a 5" diameter pipe with a 6" diameter cap bolted to the top. In theory the position of the surface monument could still be recovered by digging down to the lower monument if the pipe and cap were removed.

The MORC surveying crews usually named each station for a nearby physical feature or town. When the site for the "St. Deroin" triangulation station was selected, it was naturally named for the nearby river town having that name. The town of St. Deroin was one of Nebraska's oldest communities having been established in 1854. Its name is derived from a half-breed Otoe Indian chief named Joseph Deroin upon whose land the town occupied. A ferry operated at this location, and it would have been a stopping place for many early Missouri River travelers including those of the MORC survey crews. In 1911 the town was destroyed by a Missouri River flood.

St. Deroin as shown on an 1890 Missouri River Commission map.

To locate the monument named "St. Deroin", Nebraska surveyors Gene Thomsen and Jerry Penry made a brief search on May 20, 2005, while looking for other old survey monuments in southeast Nebraska. The St. Deroin location is in a remote area along the west side of the Missouri River about 12 miles southeast of Brownville, Nebraska, and in Indian Cave State Park which is operated by the Nebraska Game & Parks Commission. Since most of the area in the state park is only accessible by trails, the St. Deroin triangulation station was hoped to have been found undisturbed. The United States Coast & Geodetic Survey (USC&GS) had remonumented this station in 1947. During the 1947 remonumentation of southeast Nebraska triangulation stations, USC&GS had removed some the 1880's MORC cast caps from the pipes (or already found them missing) and cemented their own brass disk into the top of the pipe. This provided a more secure monument since people had been taking the 1880's caps as souvenirs. However, according to the 1947 datasheet, USC&GS had left the original MORC cap in place on the St. Deroin monument. Perhaps it was thought that no one other than a surveyor would ever venture to that remote site on private property since it was before the area was made into a state park in 1962. During the 1947 remonumentation of the St. Deroin marker, two reference marks and an azimuth mark were set by USC&GS.

When we, Gene and Jerry, first arrived in May of 2005 it was obvious that the 10-foot wide ridge where the monument resided had been converted to a hiking trail. USC&GS Reference Mark No. 2 appeared to have been struck by a piece of machinery such as a mower while Reference Mark No. 1 was found undisturbed. The MORC St. Deroin triangulation station was nowhere to be found even after using the published USC&GS distances from the two reference marks. It was concluded that the St. Deroin monument had also probably been hit by the mower on the ridge and that a worker had completely removed the "obstacle". A search with a metal locator on the ridge and up and down the nearby steep slopes provided nothing. A probe had not been brought during that initial search since we were confident that we would find at least the pipe still in place even if the cap had been taken. The hot day with temperatures in the upper 90's compounded with an infestation of deer ticks prompted us to decide to return another day for a better search.

The red triangle shows the location of the "St. Deroin" triangulation station in Indian Cave State Park which is only accessible by hiking trail. The high narrow ridges are about 75' above the floor of the ravines.


Part 2
Our Return

Our return trip to the "St. Deroin" marker occurred on April 14, 2006. Nebraska Game & Parks surveyor Rex Heiden joined Gene Thomsen and Jerry Penry during this second visit. The use of a Game & Parks 4-wheeler was a life saver in transporting the needed supplies to the marker's location for the remonumentation.

USC&GS Reference Mark No. 2 is the first marker found along the trail while approaching the St. Deroin location. The condition shows that it had been hit by a piece of machinery when the ridge was made into a hiking trail.

Reference Mark No. 2

Reference Mark No. 2

This photo is looking westerly along the high ridge while standing upon the location where the "St. Deroin" triangulation station should have been located. The blue flagging seen in the trees was placed by someone marking the trail.

USC&GS Reference Mark No. 1 found in good condition.

Reference Mark No. 1.

Reference Mark No. 1.
(Before leaving we filled in dirt around both reference marks so they would no longer be sticking above the ground).

Rex Heiden bringing the supplies with the 4-wheeler.

Gene Thomsen takes out the first load of soil after probing found the lower stone.

Gene Thomsen (left) and Rex Heiden (right).

As we neared the top of the stone we found this piece of cast iron. It is part of the original MORC cap. We theorize that when the machinery hit the monument, the cap broke and this piece fell down the pipe and rested on top of the stone.

The cleaned piece of cast iron reveals part of the word "Missouri". No other pieces were found.

This Lone Star tick was just one of many different varieties of ticks that we pulled off of us that day.

At last! The lower Missouri River Commission monument set in the 1880's. It was the first time that any of us had seen a lower triangulation stone.

Rex and Gene at the hole.

The extra work done 120 years ago preserved the location of the marker by having the lower stone monument.

A triangle appears on the stone. Also, the rust ring from the missing pipe is clearly shown.

Jerry gets into a photo.

Gene and Jerry finishing up the excavation and taking measurements.

The rust ring showing the relationship to the drill hole in the stone. Since the position of the top monument had been lost, and therefore unknown, we decided to tie out and perpetuate the drill hole which was the original intent of the MORC surveyors.

Group Photo
Rex Heiden - Jerry Penry - Gene Thomsen

The cleaned lower monument.

The folded ruler provides a reference scale for the 18" square stone. The stone surface was perfectly level - adding confidence to the work done by the surveyors 120 years earlier.

Jerry in the hole.

Rex and Jerry tying out the location of the drill hole from reference nails on the side.

Gene and Rex cutting the pipe that was placed over the stone.

The new brass disk that will mark the surface monument.

The 28" long pipe is in place. We made it short enough so it would not be sticking above the ground.

Final adjustments.

The soil was firmly packed around the pipe as we backfilled.

Ready for concrete.

We first partially filled the pipe with soil, then the rest with concrete to the top.

The new surface monument in place.

Looking easterly back over the site of the marker. When the MORC surveyors used this point there were very few trees and the view of the Missouri River must have been outstanding.

Close-up of the finished site. The marker is just below the surface for protection.

A view looking east as Gene and Rex load the tools onto the 4-wheeler for departure.

View looking south to the next ridge from a nearby clearing.

An interesting bud from a nearby tree.

The last monument to find was the Azimuth Mark that was set by USC&GS in 1947. The description said it was about 0.25 mile south-southwest from the triangulation station (unmeasured distance). The datasheet provided a much-needed azimuth from the triangulation station.

After much searching through the thick trees, a handheld GPS receiver was used to get on the right azimuth while ignoring the 0.25 mile distance. The marker was easily found once we stayed on the right azimuth. Amazingly we had already been by this marker several times which was only 25' off the trail we had traveled upon. The actual distance from the triangulation station was 0.18 mile. The view between the azimuth mark and the triangulation station is now obscured by 60 years of thick tree growth.

Close-up of the 1947 USC&GS Azimuth Mark.

Engraving of Missouri River Commission surveyors at work in the 1880's while occupying a triangulation station.

The NGS datasheet on this marker is: LF1362

© Jerry Penry 2008