The GLO as Cartographic Art

By | May 30, 2023
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Estimated reading time: 7 minutes


As a cartographer at law, I am fortunate to work with the GLO (General Land Office) maps developed for the Public Land Survey System (PLSS). Lamentably, the PLSS is the most important national governmental effort you didn’t learn about in school. The US government created GLO plats to map frontier property to sell to its growing and westward moving populace. This effort was designed to raise money for the new government. Of course there were many other political reasons for the project. But as a cartographer, I find many of the GLOs to be both beautifully crafted and a wonderful insight into our history.

The Missouri Chapter of the Trail of Tears Association is currently working to make the GLOs along the Trail of Tears available to the public. In this post are many links to start your research about why GLOs are important and why they were developed. If you learn one thing about GLO’s, it should be that they are the foundation for most of the property boundaries in the vast majority of these United States.

PLSS Map of the US


The GLOs in this collection have come from a variety of sources. However, the vast majority of them came from the Missouri Department of Agriculture’s Land Survey Index website. The Missouri Chapter of the Trail of Tears Association has paid the state of Missouri a dollar apiece. Each of the GLOs come named with a proprietary naming system, and in the PDF format. They are then processed and saved as jpegs. JPGs are easier to use in the GIS.

In the map above you see the state of Missouri and the gray lines are the modern county boundaries. The wiggly purple lines are the National Park Services map of the known paths of the Trail of Tears through Missouri. The purple squares are GLO Township borders from the Public Land Survey System. The PLSS covers the entire state, and most of the nation. However, this image show only townships that are within 20 miles of the Trail of Tears. Highlighted in blue is Township 37 North, Range 7 East of the 5th Principal Meridian. The 5th Principal Meridian is shown on the PLSS one graphic above this map.


During the processing we then assign names to the files based upon the GLO’s township and range location, and other factors. for example ‘_bw” is a black and white scan of the original GLO. “_d” means the GLO has been deprecated and replaced by a newer GLO. “_sup” means the file is a supplement to the original GLO.

File Naming Conventions: We named this file: MO_GLO_37N07E.jpg because it describes Township 37 North, Range 7 East of the 5th Principal Meridian. Click on the image to see it full size.


After the files are renamed and reformatted they are imported into our GLO geodatabase and then the process of georectifying each GLO starts. This is essentially taking known points on the GLO and pinning them to known points in our geographic information system (GIS). Think of it as rubber sheeting the GLO. It is not a super precise process but it allows researchers to get the lay of the land and understand where certain landmarks noted on the GL O might be in the real world.

GLO Sharing:

Currently we are not yet sharing the georectified GLOs on our website, or in the shared Google Drive. The goal is to share them soon, and in a way where they will almost just pop into other researchers GIS with a minimum of fuss. Also under exploration, are our options to put the GLOs up on the Chapter’s ArcGIS Online maps. All GLOs are raster images and they use up quite a bit more online maps hosting credits than points lines and polygons. The feasibility of this option is still under exploration.

GLO Status Maps:

Those of us working on this project make an attempt to keep an online GLO process status map up to date about every six months.

Land Surveyors:

The history of the expansion of the United States into the western territories cannot be fairly told without understanding the people and the mapping technology of the time. During the creation of the Public Land Survey System surveyors explored, mapped, and documented the western territories. To learn more about land surveyors you might start here: Missouri Society of Professional Surveyors (MSPS).

Down The Rabbit Hole:

So I hear you saying, “Take me on a deep dive into this Public Land Survey System, pretty please!” Here you go: A History of the Rectangular Survey System (a 776 page pdf!!!) Next, consider picking up a copy of the best book out there on Missouri’s GLOs. The map on the back cover of Professor Richard Elgin’s book The U.S. Public Land Survey System for Missouri: A Manual on the GLO System, Resurveys, Example Problems and GLO Plats Third Edition illustrates the creation of GLOs in Missouri over time. Plus, the book contains lots of interesting history I haven’t found elsewhere.

Some Beauties:

Below, I have inserted some of the GLOs I find the most attractive. Many land descriptions (maps) predated statehood. Prior to Missouri becoming a territory of the United States, and being granted its statehood in 1821, it belonged to both France and Spain. Their land settlement and development patterns greatly differed from the ‘square’ system implemented by the US with the PLSS. The French and Spanish patterns can still be seen on the land today. That’s a topic for a future blog post.

Missouri was part of the Louisiana Purchase, a transaction with France, signed on April 30, 1803. The United States purchased 828,000 square miles of land west of the Mississippi River for $15 million. That purchase includes land which would become Missouri. Missouri’s GLOs were created during the period from 1815 through the 1860s, and in to the Civil War period.

Township 27 North, Range 16 East of the 5th Principal Meridian – June 19, 1862 – Click on the image to see it full size.

Township 16 & 17 North, Range 13 East of the 5th Principal Meridian – Jan 6, 1863 – Click on the image to see it full size.

3-D GlOs?

Using Esri’s ArcPRO, we are now able to overlay the GLO maps over a 3-D terrain base. This it the NPS trail in purple overlaid on to GLO Township 34 North, Range 9 East of the Fifth Principal Meridian. Click on the graphic for a better view.

Now Go Explore Missouri’s Origins!

As of the date of this blog post we have 358 GLOs posted to our publicly shared Google Drive. Many of those GLOs are duplicates. However, we are in the process of adding new GLOs and removing the duplicates as time becomes available. Please feel free to go explore that resource and let us know if you find a beautiful GLO that should be mentioned in this blog post.

GLO Sources:

The Bureau of Land management

The State of Missouri, Department of Agriculture, Land Survey Index Prepare to pay for what should be a public record. More on that later.

Book: The U.S. Public Land Survey System for Missouri: A Manual on the GLO System, Resurveys, Example Problems and GLO Plats – Third Edition – by Dr. Richard L. Elgin (Author) (I own a copy and love this book)

Link to the GLOs in our possession

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