Armchair land exploration II

Part 2: The Past

In last week's post I provided resources for exploring our local land parcels through County records and GIS mapping system. There are also many historical resources for exploring the landscape, and this week I'll share some of them.

The Public Land Survey: or, where did all those lines on the map come from?

First of all, a couple of important questions: why are many of our land boundaries square? Who decided to divide up the land this way? You may have noticed a grid of lines on a topographic or other map. This large grid extends throughout most of the Western United States. It's a system for dividing land into parcels, and it's called the Public Land Survey System. The system arose after the Revolutionary War, when the new federal government needed to start selling off its new territories in order to pay the war debts. In order for the land to be sold, it had to be surveyed. The old European system of land surveying was called "metes and bounds," and it relied primarily on topographic features to describe the land and make boundaries. But this system isn't particularly reliable and another, more methodical system was needed.

Detail of a "metes and bounds" survey map of a California rancho

The new system relies upon a grid established upon two lines: the east-west baseline and the north-south principal meridian. Upon this framework, parallel lines of latitude are based at regular intervals, and then subdivided into survey townships of roughly 36 square miles (a square area with sides six miles long). (Note: because the earth is a curved surface, lines of latitude are not perfectly parallel to each other—they converge towards the poles, and various methods were devised to take this into account.) The boundaries of a survey township are east-west Township lines and north-south Range lines. Each township is subdivided into 36 sections of approx. 1 square mile (640 acres), and each section is further subdivided into quarter-sections of 1/4 square mile (160 acres). The federal survey only covered these quarter sections, as private surveys took over further subdivision after the land was sold.

The corners of these large divisions were (and are still) marked with monuments of various types. You may have seen one common type, which is a round bronze plaque set into the ground: there's one at Iceberg Point next to the white pillar. Often another nearby object, such as a large tree, was designated to witness the monument: thus you sometimes find a large, lone tree near a section corner called a "witness tree." Another common monument you may find on Lopez is a small bronze cover (like a small manhole) in the middle of the road. Surveyors use these monuments to set the starting point of a survey.

Principal Meridians and Base Lines of the Public Land Survey

Once this mega-grid was in place on the ground, the land could be divided and subdivided in an accurate way. The history of the western United States is inextricably bound with the land survey system: from the railroad land grants to the Homestead Acts, all development depended on the presence and accuracy of the public land survey. In the image above, you can see that not all states use the same system, but the Public Land Survey is the basis for most modern surveys.

If you've ever looked at a land deed, you might have come across something like this cryptic text: "SW1/4 NW1/4 S13, T1S R20E." This is shorthand for the land legal description, which can be translated thus: "The southwest quarter of the northwest quarter of section 13 of Township 1 South Range 20 East." (The description starts with the smallest division, the quarter-section, and goes up to the township and range level.) Within the rectilinear system of township and range, the land is usually divided into a very complex system of irregular plats and lots.

Back to Lopez

Last week I described finding a particular parcel of land that's for sale, and how I plotted it out on the county Polaris GIS map tool. Now, I can go into Polaris and turn on the Public Land Survey layer to see the section labels:

Mariner Hill neighborhood, showing parcel lines and public land survey labels.

Now that you know what "Section 23 Township 35 North Range 2 West" means, we can go looking for some sources of older maps. The BLM (Bureau of Land Management) has a collection of survey maps, some of which are from the late 1800s. So let's go here and enter the township & range we're interested in: T 35 N, R 2W (note you'll enter it as 035-0N and 002-0W; the Field Note Order isn't important). Once the results page loads, you can select the map files to view. In the Survey Plats table, click on the link in the Cadastral Survey - 1875-04-15 row (link to full image: 10.4 MB file). Here's a detail of that map:

1874 Survey map (detail)

There are cool details in this map: the wagon roads, homesteads, cleared areas, and lands set aside for military reservations... even the telegraph line! It's worth downloading these files and viewing them at full size. If you want to get the four maps for Lopez/Decatur, here's what you're looking for on the BLM site (township-range: date of survey):

The "T-Sheets"

If you want to really geek out on old maps, nothing quite beats the topographic maps made in the late 1800's, affectionately known as the "T-sheets." These maps have amazing details about the islands, including types of vegetation and the layout of homesteads down to the fields and buildings. The t-sheets are available online, but to see them full size you'll need to get a hold of a copy of them on CD-ROM (remember those?) Link to collection is here: Early Washington Maps—San Juan Islands. Library record (for Interlibrary Loan request): San Juan Islands T-sheets. Here's a delicious detail:

Update: Dr. Tom Schroeder, retired biologist at the Friday Harbor Labs, unearthed the original T-sheets and arranged to have them scanned full size by the University of Washington. Here's an article by Dr. Schroeder that reveals more about these fascinating, unpublished maps: Long-ago landcover revealed in Gilbert's exquisite t-sheets

From the Air

One last resource I'd like to share with you is a collection of aerial photos, available on the Washington Coastal Atlas Map. This map service is similar to the Polaris GIS maps I introduced earlier: you can add layers of data to the map. To do that, click the Add map data link; in the overlay window, select the Shoreline tab, then check the boxes next to the Shoreline photos dates, then click Go. The map will update and you'll see a string of colored boxes (color-coded by date) all along the shoreline of the islands. Click on a box to bring up the location info, then click the view this image or view large image link to see the photos viewer. Once you're in the photos viewer, you can navigate along the series of photos and see a larger version of each image. These images only go back to the 70s, but there have been enough changes throughout the islands to make the older photos pretty interesting. You can even compare photos of the same location in different dates!

Fisherman Bay, 1977—The Islander to Whiskey Hill.

Well, that's all I have to share today. Happy exploring, and if you have sources of old maps or photos, please do let me know in the comments!


Part one is here: Armchair land exploration.