The Sheridan Astro Station looks like an orphaned gate post or bird-bath pedestal. Skateboarders once knocked the capstone off. A USGS benchmark on top indicates the starting point for surveys that created topographic maps of much of northwest Wyoming. (Angus M. Thuermer Jr/WyoFile)

In 1896 when Sheridan was a dusty town of perhaps a few hundred people, a team of federal surveyors arrived at the Burlington railroad depot there bent on establishing the precise location of the middle of nowhere.

Sheridan was considered the middle of nowhere because two transcontinental triangulation surveys — part of an effort to determine precisely what lay west of the Mississippi — had bypassed Wyoming in favor of Montana and Colorado. As the U.S. Geological Survey sought to fill in the blank, its leader, Henry Gannett, required field workers to first establish a verified starting point that could be related to known locations — survey markers — in the rest of the country and, ultimately, around the globe.

Caped surveyors with strange looking telescopes, tripods and journals disembarking in Sheridan that summer likely contrasted with the hardscrabble residents. But by the time they completed their task, they’d proven their metle by accomplishing a feat of extraordinary precision across hundreds of miles of hostile landscape.

They laid out a network of two-dozen benchmarks — points to which they assigned global coordinates — from Sheridan to the base of the Teton Mountains in Jackson Hole. Their network became the foundation of the 7.5-minute topographical quadrangle maps of northwest Wyoming still in use today, (Yellowstone National Park was mapped starting from a point in Montana) part of a Geological Survey campaign to map the nation. The government completed that job in 1992, just 9 years before Google Earth made topo maps almost obsolete.

In 1896, federal surveyors spent six weeks establishing the longitude and latitude of the benchmark atop the pier at the Sheridan Astro Station. From there they surveyed and established 24 other survey stations over 198 miles of rugged landscape to the base of the Teton Range in Jackson Hole. (Angus M. Thuermer Jr/WyoFile)

Today anybody with a computer can see a satellite image of the tree that’s grown over the monument where the 1896 survey began. It’s a brick pillar slightly higher than three feet, at the corner of Sheridan’s Crook and Fourth streets. The Sheridan Astro Station monument is largely forgotten. It looks like an orphaned gatepost and has been used as a pedestal for a birdbath. At one point, skateboarders grinding on the pillar knocked off its eight-inch thick capstone. But the monument still stands and has launched pilgrimages by history buffs.

120 years earlier it was the starting point of an entirely different kind of expedition, one in which USGS surveyors crossed 198 miles of untracked mountains and hilltops. Their route took them from Sheridan to Jackson Hole where double checking revealed their measurements were off by only 8 and 11/32nds of an inch.  

Six weeks of stargazing

The remarkable accuracy of an 1899 map of Jackson Hole launched Jackson surveyor Todd Cedarholm’s pilgrimage to Sheridan. You might call Cedarholm, the owner of On Sight Land Surveyors, Inc., a cartophile — one obsessed by and in love with maps. When he got to Sheridan he found the monument very much the way surveyors first described it in an annual report — “a solid column of cemented brickwork, 2 by 2 1/2 brick-lengths in cross section and 3 feet in height … capped by a dressed stone measuring 8 by 20 by 24 inches.” Constructing it was their first task. Atop it they centered and embedded a benchmark.

Next, they had to determine where exactly it was.

Doing so was a leapfrog affair. One method of determining where it was would have been to survey from known points hundreds and hundreds of miles away. A faster method was for surveyors to search out known stars with their transits — powerful telescopes with reticles or crosshairs — and measure the stars’ angles above the horizon. The monument pier and benchmark served as a platform for these transits.

Because the crew would spend weeks at the Sheridan monument, they constructed a hut over the pier, with a north-south slit in the roof, Cedarholm said. With all that assembled, the crew’s first task was to determine the orientation of a true meridian — a straight line through the benchmark that ended at the north and south poles.

Establishing a meridian was a relatively simple task, as was the next step — discovering the latitude of the Sheridan monument. It’s done by picking a pair of known stars — one north and one south of the zenith of the astro station — and comparing their angles above the horizontal plane when they passed the meridian. Books and tables provided the star pairs, methods and formulas.

All of this was done at night and so stargazing was the genesis of the Sheridan station’s moniker. The survey crew, Cedarholm observed, “were astronomers more than they were surveyors.”

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But determining longitude of the Sheridan Astro Station was more difficult. For this, the crew employed a specialized three-foot long “meridian transit.” As its name indicates, this telescope could point only along the benchmark’s north-south line.

Surveyors would position it in anticipation of a particular, known star crossing its path. When that star lined up in the crosshairs, a surveyor would note its elevation, or vertical angle, and the time. Using formulas, one could calculate how far east or west the Sheridan Astro Station was located.

But the time had to be extremely accurate, and the watches of the day were not up to the task. That’s why Sheridan, a town that was reached by a rail line only four years earlier, was so important.

Along with the railroad came a telegraph wire. Surveyors built the monument 400 feet from the depot so they could connect with colleagues at an observatory in St. Louis, 962 air miles away. Not only were the St. Louis observatory coordinates precisely established, but observers there kept the exact time. With such resources, Sheridan surveyors could eventually determine the longitude of their monument.

But all that timekeeping would take time — six weeks in fact. “These guys had a lot of patience,” Cedarholm said.

Surveyors located the Sheridan Astro Station near the railroad line and Burlington depot so they could connect to a telegraph wire and know the exact time, a critical variable in determining longitude. The historic Sheridan Inn stands behind the passing train and next to the depot. The pier has weathered passing trains, resting birds and youthful skateboarders for 120 years. (Angus M. Thuermer Jr/WyoFile)

Here’s how it worked. The teams in St. Louis and Sheridan would coordinate regarding what stars they both might observe on a particular night. Using various telegraph codes and patterns, surveyors would compare when a star crossed the known St. Louis meridian with when it crossed the unknown longitude at the Sheridan Astro Station.

The surveyors made their observations at both points on the same nights, coordinating and communicating the exact time over the telegraph, Cedarholm said. The time it took the signal to cross hundreds of miles of copper wire was insignificant. Harder to compensate for was the “personal equation,” or how quickly individual telegraphers could hit the key.

The sky had to be clear at both ends of the system and the telegraph wire had to remain intact. “They were really lucky if it worked at both places,” Cedarholm said.

The 1896 field crew determined the Sheridan Astro Station was at 44 degrees 48 minutes 31.10 seconds north latitude, plus or minus 0.12 seconds; 106 degrees 56 minutes 45.21 seconds west longitude, plus or minus 1.16 seconds.

Baseline to baseline across 198 miles

The 1896 surveyors had to establish more than a single point at Sheridan, however. To accurately map the region cartographers needed a network of about two dozen fixed points between Sheridan and Jackson Hole, most on mountaintops.  

Surveyors created such networks using triangulation, a mapping system in which multiple survey points are related to one another as a series of connected triangles. Distances — sides of the triangles — are calculated using “classical spherical geometry,” Cedarholm said. In such networks, however, it’s critical first to establish a baseline — one precisely measured side of one triangle.

For the network starting in Sheridan, the surveyors went a short distance to Ranchester where the Burlington and Missouri Railroad ran along a relatively straight and even grade for about five miles. They brought out a 300 foot steel tape. Even the heat of the day could expand the tape and result in inaccurate readings.

Consequently, “measurements were made at night, or during light rains, to avoid so far as possible errors…” the 1897 report said. “Temperature was taken by two thermometers at each tape length.”

Once the survey crossed the mountains to Jackson Hole, surveyors established a second roughly 5-mile baseline at a meadow now known as Baseline Flat. Now it was possible to measure the Teton baseline two ways. One was to take all the readings from Sheridan — 198 miles and 24 mountaintops away — and calculate the baseline length using classical spherical geometry. The second was to mow a path through the sagebrush, get out the 300-foot steel tape and thermometers, and measure the baseline directly.

They did both.

The two measurements of the Teton baseline came within 8 11/32 inches of one another, according to computations made from metric survey reports. That amounts to an error of 1/34484.

What would a contemporary measurement be, Cedarholm wondered.

Surveyor Todd Cedarholm tracked down the Sheridan Astro Station, which the federal government officially classifies as destroyed, and hopes to preserve it and re-list it as an verified benchmark. (Angus M. Thuermer Jr/WyoFile)

He took his modern tools to the Teton baseline and measured it himself. “My GPS measurement fell between the two,” he said.

It’s unremarkable that 1896 surveyors could measure a five-mile line with a steel tape and come close to a contemporary measurement. But being able to come within 9 inches of calculating that same distance from 198 miles and 24 mountaintops away reveals the accuracy of the 1896 team and its equipment.

Somewhat confounding to Cedarholm, however, is the actual location of the Teton Baseline — and the Sheridan Monument — on the globe. While the surveyors were precise in their 198-mile exercise, they were less exact in pinpointing the starting point at the Sheridan Astro Station.

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Ultimately, the Astro Station — and the corresponding Teton Baseline — are some 1,000 feet off from where the 1896 crew calculated them to be. Most of the difference is in longitude, Cedarholm said. He observed that difference only after setting his GPS device on the Jackson baseline and near the Sheridan monument for several hours each. (Cedarholm couldn’t receive GPS signals at the Sheridan Astro Station because of the overhanging tree, so he computed and corrected from just across the street.)

“I was kind of disappointed,” Cedarholm said. But when put in the context of the entire globe, a 1,000-foot deviation is akin to the few inches difference between the two 1896 Teton baseline measurements.

For the record, Cedarholm calculated the Sheridan Astro Station at N 44 degrees 48 minutes and 21.26463 seconds north, 106 degrees, 57 minutes 5.48893 seconds west.

One crucial piece of topographical information remained to be determined, however — elevation. But that wasn’t in the 1896 job order and it’s not part of the story of the Sheridan Astro Station.

Officially, the USGS lists the Sheridan Astro Station as “presumed destroyed.” But the pillar at corner of Crook and Fourth streets in Sheridan stands proud, and Cedarholm hopes to officially reestablish it with the government as a monument to the middle of nowhere.

This Google Earth image shows the corner of Crook and Fourth streets in Sheridan and the tree (center) shading the Sheridan Astro Station. The USGS completed its job of mapping the country with 7.5-minute quadrangles in 1992, 9 years before Google Earth made them almost obsolete. (Angus M. Thuermer Jr/WyoFile)



Angus M. Thuermer Jr.

Angus M. Thuermer Jr. is the natural resources reporter for WyoFile. He is a veteran Wyoming reporter and editor with more than 35 years experience in Wyoming. Contact him at or (307)...

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  1. Nice story and great insights – thank you WyoFile. Perhaps George Clooney’s character, Ulysses Everett McGill, in the movie ‘O Brother, Where Art Thou’ said it best: “Well, ain’t this place a geographical oddity. Two weeks from everywhere!”

  2. Correction to my comment:

    The 1892 longitude at the US Naval observatory is 3″ different to GPS.

    So was the longitude of the Naval observatory “off” 3 seconds?

  3. I am curious about the accuracy statement of the 1896 survey. 0.12″ Lat and 1.2″ Long.

    Firstly, their position was astronomic. Deflection was known to occur, but not quantified. So, the comment stated that they off a1000 feet, “mostly longitude”.

    Was the GPS latitude first corrected to astronomic latitude for comparison? And how much difference in astronomic latitude was there in 1896 survey compared to astronomic today?

    Second. The longitude of Sheridan was “relative” to the St Louis observatory. Again, astronomic. And the st Louis observatory’s longitude would’ve been relative to the Naval Observatory in Washington DC.

    So, was the 1.2″ estimated error relative to Washingtin DC? Or to St Louis? And, which longitude of the Naval Observatory was used? The longitude of the Naval Obs. was revised several times.

    Notably the 1892 longitude of the naval observatory is 5″ different to GPS.

    So, I think saying that the 1896 survey is “1000 feet off” is very misleading and unqualified. Unless deflection and datum transformations were applied, not mentioned in the article.

    I suspect that a review of the data will show that the survey wasn’t off anything approaching 1000 feet.

    I suspect, an academic review would find the 1.2″ by 0.12″ stated accuracy, a reasonable estimate.

    No, the astronomic position of Sheridan by the 1896 survey was probably far better than a 1000 feet.

    1. Larry, you are correct, our survey consisted simply of determining a modern Lat/Lon at Sheridan and at the Teton North Base in Jackson Hole and then comparing the ellipsoidal distances between the 1896 triangulation and the two OPUS positions. the difference between those two is about 1000 feet over 198 miles. Comparing a modern geodetic position to a historic astronomic position is comparing apples to oranges.

  4. In the last 40+ years, every time I see a surveyor, my lot shrinks. Do surveyors calculate the ever changing magnetic declanation? Or does that not make any difference? My town lot is down to 43’x138′ from 50’x150′. I’m afraid it might disappear from under me.

  5. Very interesting article of land surveys done properly. The accuracy attained by honest hardworking 19th century surveyors cannot be understated . But as the vast American West was diligently delineated by survey crews and their maps became vital public records for establishing land lines and property boundaries , some human nature crept in to taint the process. Accuracy was traded for expediency in some cases, and some good old fashioned corruption prevailed . To Wit: a lot of fraudulent surveying.

    Instead of using precision instruments and meticulous double-checked traverses , dubious crews contracted by the government would just rough in the land corners with a hand compass, pacing across the landscape to approximate a corner. Sometimes these freebooters would use nothing more advance than Dead Reckoning to plot and plat the open lands. The worst of them did their ” surveys” from local saloons and turned in their fraudulent worksheets for payment, having never set foot on the township and range lines.

    Get out a topo map of the lands west of Meeteetse in my Park County. Go about 16 miles up the Greybull River Road to the main Pitchfork Ranch headquarters , ( the Z Bar T ). Just before the concrete arch bridge you would cross the north-south line that separates Range 102 from Range 103 west, and a mile up that line you come to the boundary of Townships 47 and 48. So far so good. But keep going north along the range line and you hit the anomaly…Township 48 -1/2 North. Section 1’s northeast corner is a thousand feet south and 4000 feet west of where it should be in meeting Section 36 of T.49 R.103 That is what is known in the surveying world as a “Bust”. A big one. In fact, every township, range, and section line in all directions reckoned by the Rose VABM triangulation point is ridiculously off. In order to begin rectifying this wretched mess, the Department of Interior’s USGS + BLM created Township 49-1/2 north, a rectangular sliver of demarcated land along the foot of Carter Mountain that is a monument to fraudulent surveying . But not until the compounded error had real world consequences.

    Oil company Land Men were not born yesterday . They know how surveying works ( or doesn’t) and how to leverage the land lines and surveys to their advantage. They saw an opening up there on Rose Creek below the rims. Prior to creation of Township 48-1/2 North , there was a bona fide No Man’s Land up there… land that was outside of any legal descriptions on the books at the Courthouse or Statehouse or wherever the Feds keep their certified plats and official maps. Sure as snake oil, a wildcat oil rig showed up on the flanks of Carter Mountain in No Man’s Land. The rig’s location for legal purposes was…anywhere they wanted it to be. For royalty purposes , access, permitting , or otherwise. While the rig’s geographical coordinates could be precisely known ( latitude-longitude ) to five decimal places, the map tack for it’s legal location metes ands bounds or whatever could be put anywhere in the Phantom Zone . The maps are made of rubber up there. Establishing a fractional township did not fix the issue, it merely filled a void. The major landlines up there are still badly skewed, and resurveys are expensive. A 1980 consequence of an 1890 fraudulent survey.

    I was a land surveyor for 12 years. Getting maps and legal descriptions to fit the actuality on the ground was a constant challenge. Land corners and survey markers have of way of moving when nobody’s watching.

    1. This was a good article and your comment is enlightening. I always wondered about the township slivers, odd sections and some fences that align to a west declination instead of east around Pinedale. Maybe they were done from a barstool as well.

      1. Tim, actually the fence issue is only rarely a result of a bonafide fraudulent survey. The original government survey contracts only required that the surveyor place the exterior corners of a section. As those sections were “broken down” or subdivided into smaller aliquot parts and sold it was usually without the benefit of a survey. Fences followed, again without a survey, so problems arise. It’s one of the biggest challenges surveyors face today is to sort out old fences and ownership. However, it’s rare that a fraudulent survey is the problem.