Layers of Borderlocking

On February 28, 2010 · 11 Comments

Is Borderlock (-ed) (-ing) even a word? I don’t think so. "Landlocked" is a perfectly fine word but it doesn’t quite cover the situation I’m attempting to describe. I noticed a query that arrived recently on the Twelve Mile Circle from a user of a well-known search engine and it piqued my curiosity.

I’ve started many an article with a lead-in just like that. Truthfully, this is a great idea generator and an occasional benefit that comes with checking the access logs each day. Sometimes the fishing net drags-in an unexpected haul that results in an article. This time the search term seemed rather innocuous but it entertained me for several hours: "how many Maryland counties border another state?"

I know, I’m easily amused. It’s a gift.



View Larger Map

I though first, well almost all of them since Maryland is small, skinny and irregularly shaped. However, what does "border another state" actually mean? Certainly counties sharing a land border with the state boundary count towards that tally. I suppose a case could also be made for waterborne boundaries, and in this instance Maryland owns the Potomac River up the the shoreline of Virginia. Thus all Maryland counties except Anne Arundel, Calvert, Talbot and the the City of Baltimore (independent and considered a "county equivalent" — but not to be confused with the County of Baltimore proper).

Then I started having some fun with it and began to wonder, what would happen if I expanded the definition to also include counties that had direct access to the sea. Thus, are there any truly "borderlocked" counties within Maryland? Those would be counties that neither touch a state border not have a reasonable outlet to the sea. They would have to be completely enclosed within the interior of the state. Trapped. Make that slight change to the definition, note that Baltimore City, Calvert and Talbot all have direct access to the sea, and only Howard County remains totally borderlocked.



I took it a step further. How many levels of borderlocking exist for each of the fifty states? These would be instances of one or more borderlocked counties hemmed in by a ring of borderlocked counties, then surrounded by another ring of borderlocked counties, and so on. It’s kind-of like a double landlocked country but a little different. Maryland, as we just observed, has ONE level of borderlocking. Travel from borderlocked Howard County to any of its neighboring counties and one will find direct access to the state border either by land or by sea.

In homage to my obsessive-compulsive side, this is what it looked like for all fifty states.


Level of County Landlocking by State

Indeed, I colored each of the 3,000+ counties in the United States on this map to determine the level of borderlocking for each state. Now, in my defense, it didn’t take very long. I could have been excessively precise but I guessed liberally when it was close. I am sure there are errors contained here but I have a life so I didn’t spend hours obsessing over exact precision (hmm… just spotted one now but I’m too lazy to go back and fix it). I also discovered that this method of mapping was fairly self-healing: an error might impact the coloring of one or two counties but it usually didn’t change the formation of subsequent ring(s).

By the way, feel free to right-click the image and open open it up in another tab if you want to see it in greater detail. I shrunk it down to fit within the confines of the blog template but the full-sized image has already been read by your browser and still lurks behind the scenes — I simply adjusted the width and height of the image tag in the underlying HTML code.

The various states fall into ranges. There are some states like Connecticut (sorry, CTMQ), Rhode Island and Delaware that have ZERO borderlocking where every county straddles the state border, either by land or by sea. The greatest extremities exist in Georgia and Kentucky with four levels of borderlocking, plus the Grand Champion found only Texas with an astounding FIVE levels of borderlocking. That’s right, there are select people in Texas who would have to cross through a minimum of five counties before hitting the state border.

Apparently that wasn’t enough for me. I had to discover the most borderlocked counties in the United States overall rather than by individual state, so I produced the following map.


Level of County Landlocking in the United States

Before I looked at the resulting data I have to say that I appreciated the map first on an artistic scale. It reminded me of the inside of a geode; morphing and changing as it drew closer towards the center. I found myself staring at the image on its own terms as much as I pondered the geographic implications. It’s kind-of mesmerizing.

What this says, assuming I’ve drawn and counted this correctly, is that there are only SEVENTEEN layers of borderlocking for the collective counties of the United States. Think about it. Nobody, ever, is more than seventeen counties away from an international border or the sea. That extreme definition applies only to a scattering of counties in eastern Kansas plus one lonely county in far southeastern Nebraska. Most people are considerably closer.

A traveler could and probably would take a more circuitous route involving many more counties unless he wanted to undertake this trip on foot. However, in theory at least, he could reach a land or sea border by traversing seventeen counties or fewer depending upon his starting point. Can it be done by automobile? I’m not sure. The path would need to avoid places where the layers meet at a single point (e.g. square counties connected on a diagonal). I think I see a possibility heading from eastern Kansas towards the general direction of Lake Michigan. Maybe I’ll save that puzzle for a future article if people seem interested. Maybe someday you’ll earn the bragging rights by being the first person to drive it!

This isn’t what I expected to find at all. Thank you random visitor who had no idea that I’d latch onto it somehow and take it down this path.

On February 28, 2010 · 11 Comments

11 Responses to “Layers of Borderlocking”

  1. Randolph Clark says:

    I may have to take issue with one statement. It’s where you say you have a life.

  2. Greg says:

    That IS mesmerizing. Did you whip up an algorithm to do the grunt work (especially for the national map) or did you eyeball it? I have a small quibble about your treatment of Lake Michigan as a de facto international border, but…wow. Excellent work. Now if only Google had county borders on their maps…..

    • Randolph: OK, half a life. 🙂

      Greg: I was considering Lake Michigan under the "direct access to the sea" exception. I know that leaves me vulnerable to thoughts such as, “does this mean the Mississippi River all the way up to Minnesota counts under that exception, too?” All I can say is that I was pretty free and arbitrary in the way I assigned the rules.

      I did the design work by hand. Sometimes the low-tech approach produces the quicker answer. It took maybe an hour for each map… not so bad.

      • David/Wm_O says:

        Ask, can a sea-going ship touch that county? Lake Michigan yes. The Mississippi River above New Orleans, I haven’t heard of it. Two big changes: Portland OR is a sea-port. 2) Henry Hudson sailed his boat all the way up to Albany. How high do sea-ships go on the Hudson River today?

  3. Tor Lillqvist says:

    I wonder if it is a coincidence that (to an outsider) the degree of border-lockedness correlates with the (perceived) degree of xenophobia and backwardness of the locals? (I’m not serious, of course, and there are lots of counter-examples.)

  4. Alger says:

    Needlessly Technical and completely moot point. Connecticut hasn’t had functioning counties since 1960.
    http://en.wikipedia.org/wiki/List_of_counties_in_Connecticut

    Since the geographic units still exist your work here isn’t “wrong”, and since they all have the same first order border class this doesn’t change a damn thing on any map except the last, where consolidating CT changes the class of Duchess County, NY, and its bordering counties shift accordingly in a limited way.

    This reminds me of that old brain teaser: What state has the highest percent water boundary?

  5. mike says:

    Excellent work!

    As I’m sure there is some way you could turn this into a process, I agree: sometimes its better to just do it by hand.

    Tufte would be proud!

  6. mike says:

    Next up: try it with Minor Civil Divisions (towns, cities, boroughs, parishes, townships, etc)

  7. Steve_CTMQ says:

    You’ve outdone yourself with this post. Most excellent.

  8. Joshua says:

    Agreed, very excellent!

    Wondering about how to do it in GIS, I guess some sort of buffer function. Maybe I’ll figure it out once I finish relearning it.

  9. David/Wm_O says:

    I suppose/suggest that “The sea” could be understood by answering the question “Can a sea-going ship touch that county (safely or unsafely (wreck!))?” So Lake Michigan qualifies as sea-going. New Orleans qualifies as sea-going ( but was sea-worthy anyway ). I doubt that further up the Mississippi counts; I haven’t heard of sea-ships going any higher than New Orleans. Perhaps the “biggest” change would be with Portland OR, which is a sea-port.

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