Gaps on the Map: Pueblo, Colorado to Cheyenne, Wyoming Beacons

1930 Pueblo—Cheyenne: Excerpt of a beautiful hand-drawn map
1930 Pueblo—Cheyenne: Excerpt of a beautiful hand-drawn map
I received the following fascinating information from website contributor Jeff Johnson. He has used two airway maps to estimate the positions of beacons that don’t appear in the NGS database, and therefore for which we have no location data.

I’ve added the actual coordinates as indicated on the NGS datasheets where they exist. I also found two arrows thanks to Jeff’s work—can you find more? Leave a comment if so!

In addition to Jeff’s description, below, of his method and results, I’ll include his insightful comment:

What fascinates me most about these beacons is that you and others seem to be inferring their positions from secondary data: that if there ever was an exhaustive and official book or list published by the airmail service, it is either lost, or waiting to be discovered in some library basement. That a nationwide system could be implemented, and then more or less lost, within a few decades, along with any documentation that might have once existed, is fascinating.

Jeff searched the Coast Survey’s Historical Map & Chart Collection using their “classic” search: Office of Coast Survey Historical Map & Chart Image Catalog

The chart Jeff used to develop the table below is listed as chart #131, Airway Map Pueblo Colorado to Cheyenne Wyoming, 1930.

Subsequently he found another version of the map from 1928. (The 1930 version is available at the Library of Congress and is included in my index to their airway map collection, but the 1928 map is not.)

Jeff writes:

This one chart shows some 30 beacons in eastern Colorado and southern Wyoming, only 11 of which seem to correlate with your lists of PID numbers. I decided to attempt a spreadsheet of latitudes and longitudes by measuring on-screen pixel distances to the parallels and meridians shown on the chart, and interpolating.

The beacons numbered 0? to 20 run south-to-north on a line that roughly matches today’s Interstate 25. Beacons 37 to 44 run west-to-east across southern Wyoming. I actually think that, given the large scale of the chart, my interpolation method should fix coordinates to an accuracy much better than 500 meters, perhaps 50 or less. But when I compare my values against those from your PID tables, where they exist, they aren’t quite that good. One possibility is that latitude and longitude were referenced to a slightly different global datum than that used by today’s GPS. Another is that the charts, although superbly drawn, are nevertheless hand-drawn. This is evident when they are compared to charts published just a few years later.

There is the odd case of beacon #6 near Monument CO: I’m sure your PID file has it located properly, because although the arrow is long gone, there is a long area of concrete rubble visible from satellite. Also, the fact that the road that runs next to this is apparently still known as Beacon Light Road is definitely a clue. But the position of #6 on the 1928-30 charts is several Km off. I can only conclude this is a charting error. How it wasn’t discovered in the two years between is odd though. Both charts are marked “Advance Sheet — Subject to Correction.”

Beacon #8, near Castle Rock CO, seems needlessly mysterious. The 1928 chart shows it, but it’s not on the 1930 chart. Instead, the 1930 chart shows two others, labeled 8A and 8B. All three are in a tight little bunch. It’s like someone kept tweaking the location: “No, I think it should be a little more to the left.” I wonder what might have been going on.

The I-25 corridor is considerably more built-up today, and most of the sites in my table seem to be under modern concrete or structures. I’ve never done any field work on this remarkable little side bar of 20th century archaeology: only looking at satellite views, and I’m probably not the best at interpreting these.

This is all from just one chart. I hope you or someone else may find this archive of aeronautical charts a useful additional source of candidate sites for exploration (if you weren’t already aware of its existence). It does, however, demand some time and effort to do the pixel-counting and interpolation of coordinates.

I’m just fascinated by the interactive map on your web page: not so much the lines of dots, but the gaps in the lines of dots.

StateCityLegendBeacon #Coordinates (Interpolated)Coordinates (Actual)NGS PIDNotes
COPueblo2 LF0?38.2527, -104.6367
CO138.4075, -104.610438.400627,-104.615438JK1093
CO1 LF238.5337, -104.6484
CO338.6975, -104.690438.690014,-104.696597JK1181
COColorado Springs2 LF438.8202, -104.7053
CO538.99, -104.813638.991679,-104.812878JK1199Concrete base remains
COCharted off position?1 LF639.0653, -104.848639.122724,-104.867966KK1650Along Beacon Lite Road
CO739.2654, -104.8819
CO1928 Chart1 LF839.4223, -104.864
CO1930 Chart1 LF8A39.3303, -104.8851
CO1930 Chart8B39.3763, -104.8614
CO939.5088, -104.8839
CO1039.6293, -104.8956
CODenver2 LF11?39.7628, -104.8611
COUnmarked Beacon?3 LF39.7609, -104.8924
COUnmarked Beacon?39.7525, -104.9935
CO1239.9167, -104.8516
CO1 LF1340.0837, -104.7875
CO1440.2723, -104.8126
COGreeley2 LF15?40.4017, -104.686240.397018,-104.690711LL1223
CO1640.5847, -104.730840.581291,-104.730876LL1260
CO1740.6988, -104.77340.704521,-104.780116LL1264
CO1 LF1840.8308, -104.804540.826392,-104.810442LL1277
CO1940.9754, -104.813840.989763,-104.801369LL1272Concrete base from generator shed remains
WYCheyenne2 LF20?41.1596, -104.813
WYLaramie2 LF3741.287, -105.5816
WY3841.2713, -105.440341.267875,-105.433681MO1245Arrow and concrete foundation of generator shed intact
WY3941.2281, -105.246941.226233,-105.243205MO1218Arrow intact
WY4041.1984, -105.048941.196879, -105.047821Arrow intact
WYCheyenne2 LF41?41.1596, -104.813
WY4241.165, -104.662641.164783, -104.674532Arrow intact
WY4341.1856, -104.51141.181384, -104.503738Arrow intact
WY1 LF4441.1815, -104.3281


  • 1 Department of Commerce Intermediate Field (an emergency field for mail planes?)
  • 2 Commercial or Municipal Airport
  • 3 Army Navy or Marine Corps Field
  • LF Lighting Facilities

Posted on

by Zhanna

| Tagged: airway beacons

3 thoughts on “Gaps on the Map: Pueblo, Colorado to Cheyenne, Wyoming Beacons”

  1. I believe I have located several missing from your inventory, one north of Castle Rock and another near Larkspur. The Larkspur unit is in a “People of Douglas County” history book and listed as on the Hunt Ranch Butte. The entry reads: “The beacon on Hunt Butte was powered by a gasoline engine operating on a time clock. Sometimes the clock got out of order and while it was being repaired, the engine had to be started by hand. Alice, Margaret, and I too turns riding horseback the eight or nine mikles roundtrip morning and evening to start or shut the engine off”.

    Could I get a copy of the Jeff Johnson map collage. If i had it, I might be able to locate more of the missing beacon/locaions in my area?

    All the best!

    • Hi Joe,

      You made a request for a “collage.” Sorry, but there isn’t any. I compared two airway charts, from 1928 and 1930, to estimate latitudes and longitudes. Zhanna has links to both. The only significant difference between the two that I’ve found concerns the beacons near or atop Castle Rock. The three Castle Rock beacons, 8, 8A, and 8B are in a short line roughly north-south, with 8B in the middle. I’m guessing from the article Zhanna found that 8A, at the south, may have been on top of the rock itself.

      I was delighted that Zhanna immediately found two previously unknown arrows in southern Wyoming. I’m still kicking myself that I didn’t spot them in satellite views myself. In both cases, they are in plowed fields, and the farmers seem to be going out of their way to preserve the remnants: plowing around them, when they could probably save time and effort by just ripping them out.

      Best of luck!

  2. I can’t explain the mystery surrounding 8, 8A, and 8B. But I noticed that the nearby landmark Castle Rock looked like a good spot for a beacon. I found the following article from April 19, 1929:


    The million-candle power beacon light which the government is having installed on top of Castle Rock, will be connected with the Commonwealth Company’s lines this week and put into service. This light is being installed in connection with the government’s Cheyenne-Pueblo air mail route to guide the mail pilots during their night flights. The beacon, from its vantage point on top of this historic rock will cast a beam of light which may be seen for many miles in all directions round about. Besides being of inestimable value to night flyers on the government air mail routes, the beacon will draw quite a lot of attention to Castle Rock from those passing this way.


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