PLSS?
Yes, the US Public Land Survey System, the starch, the superglue, the permanent hair spray, which along with Canada's Dominion Land Survey (DLS), holds together central and western North America's grid roads and checkerboard farm fields.
Well it just so happens that these person-sized historical monuments from 1891 are positioned at PLSS intersections. So let's get to work finding which ones are still there, and putting them on OSM!
Where to start? East end, west end, middle?
We'll start on the west end (Montana / North Dakota / South Dakota tri-point, highest numbered Terminal Monument 360M) and work backwards (east).
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Drier climate, less chance of a tree blocking aerial view.
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More pasture and range land. Less tractor farming. More chance a monument is still there.
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More wild west scenic badlands, less boring flatland farms. Fun even if you never leave your armchair.
Choose USGS Topographic Map background layer
![[Image: OSM editor]](editor0.jpg "OSM editor")
You notice that we have selected the USGS Topographic Map background layer there in OSM's iD editor. You will also notice that we are in luck today: the particular USGS quadrangle we are looking at is showing Monument 309 (309 miles west of Minnesota), at an elevation of 2606 ft.
Normally we would see the PLSS section line extending north, colored red. But in this case there is a dirt road covering it up.
We do see the black state line passing exactly through Monument 309, as it should.
Ignore South Dakota
From 1891-92 the monuments along the border were placed on North Dakota PLSS section corners -- not South Dakota's -- and every half mile in between.
Thus even though on the USGS map you may see red lines extending both northward and southward from the state line, you need to ignore the southward ones. Same with fence lines: a fence coming from the north might run along a North Dakota PLSS section or half section line. One might expect a monument near where the fence hits the state line. On the other hand, pay no attention to fence lines coming from the south. They would be South Dakota PLSS-based.
So even if you see a bright fence post big enough to be a monument, if there is only a single tell-tale fence leading southwards from it, ignore that potential monument.
Place temporary markers every mile...
In the (iD) editor click on "Point" and place empty points every mile, at the intersections where the red section lines coming from the north, not south, hit the state lime. Do this not for the entire 360 miles (720 markers) but just for one screen's worth, perhaps three markers (three miles).
... and half mile in between
How to locate the half miles?
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Use iD's Measure tool, or:
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hold a piece of paper on the screen and make a mile mark, then fold the paper in half... By the way:
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often half mile fence lines appear with red dashes on the USGS map. If it looks halfway between sections it probably indeed is.
Switch to aerial imagery and confirm monument existence
So now in the (iD) editor we select whatever clearest aerial imagery that is offered, and see if we can locate a bright pillar with a noticeable shadow (depending on the weather at imagery acquisition), somewhere near (or even underneath the icons of) our temporary markers.
Toggle between USGS and imagery backgrounds
In iD be sure to also try CTRL+B,
to toggle back and forth between USGS Topographic
maps and imagery backgrounds.
Insert tags and save
Amazing, we actually found a monument. We fill out the tags. Perhaps something like:
historic=monument material=quartzite name=North Dakota - South Dakota boundary monument 276 start_date=1891 wikimedia_commons=File:19940805nsdak.jpg man_made=survey_point Etc.
Now remove any leftover temporary markers and press Save. You should see "You just edited OpenStreetMap!"
We can even generate link files
Besides the red lines on the map, the US Bureau of Land Management (BLM), and State of North Dakota also offer downloads of PLSS geometry. Via clever post-processing we determined which of the nodes of a section ring were the SW and SE corners and their halfway points, and created link lists like 359½ 359 | 358½ 358 | 357½ 357 | 356½ 356 | 355½ 355... Clicking on such links brings you to the general location in the OSM (iD) editor where a monument is supposed to be.
The fact that iD lacks a crosshairs to show the exact position of the URL given can be forgiven, as we don't have a very exact position to offer it anyway.
Take Monument 276, our background photo. Even if there were no weeds and all background layers showed it, the white blip would still be in slightly different positions.
If you get as far east as the Sisseton Reservation
![[Image: Western boundary of Sisseton Reservation]](r0.jpg "Western boundary of Sisseton Reservation")
Note from mile 44.5 to mile 12 the boundary crosses the wedge shaped Lake Traverse Indian Reservation (Sisseton Indian Reservation on maps), with its different grid and interesting story as to why.
In the image we computed potential monument points eastward up to Monument 45 (elevation 1631 ft.). East of which, at what would be mile 44.6, we hit the Sisseton Reservation's dashed black diagonal western boundary. We know that the monument at elevation 1714 ft. is Monument 44½, and the one at elevation 1733 ft. must be Monument 44. Now all we need to do is check the aerial imagery to be sure they are still there. (In fact the North Dakota red PLSS section lines still indeed do connect to the monuments, even on the Reservation, but they need to be traced from the north, southward into the Reservation.)
Other uses of PLSS data
Yes, even house numbers are often ultimately PLSS-based! Now that you know the underlying system (USA: PLSS, Canada: DLS,) behind all those rectangular roads and administrative boundaries (except Texas: rectangular yes, but not PLSS,) next you could learn about correction lines...