zev, you do seem to be correct:
http://www.njhm.com/delaware.htm
What makes things confusing is that many maps show the boundary going down the center of the river/bay, but it follows the mean high water mark since 1934. Interesting but odd stuff. The landfill is at Finn’s Point.
My first attempt at posting this ended up in the ether…
Russia has Kalningrad and Malaysia two non-contiguous chunks of Borneo.
Bosnia and Herzogovina has a small strip of alnd - 23 km - that cuts Croatia in two at the city of Neum.
Texas’s current borders are largely a result of our joining the US. If you ever find a map of the Republic of Texas, it’s amusingly large and reach-y, including parts of Oklahoma, Kansas, Colorado, Wyoming(!), and New Mexico, not to mention areas south of the Nueces River and west of the Sabine River down to the Rio Grande (these two rivers were the borders of the province of Texas in Mexico). IIRC, when the US annexed Texas, they set the boundaries more or less where they are today.
The Mexican-American War started when US and Mexican forces got into a fight in area that we both claimed (south of the Nueces and north of the Rio Grande). There was some dispute as to exactly where the fighting started (some Northerners and Whigs, such as Abe Lincoln, suggested that the US troops might have been south of the Rio Grande looking for a fight). Long story short, the US won, setting the southern border of Texas at the Rio Grande, and annexing the claimed parts of the Republic of Texas that would later become parts of other states, presumably as part of the deal for assuming Texas’s debts.
I understand there was a minor border conflict with Oklahoman settlers at some point, and recently the New Mexico government found that a narrow strip of land south of New Mexico in Texas was apparantly supposed to be part of New Mexico but became part of Texas due to a clerical or survey error of some sort. Not sure if anything will come of that.
Many borders which follow rivers get weird over time. If the river changes course, the original border stands. This can lead to a very strange situation.
I suspect this depends on the jurisdiction, and whether under the law of the territory in question the border remains as the river path, or as the line on the map.
If you really want to go to town on exclaves and enclaves, the Dutch-Belgian border is a jigsaw of them, with areas of one country surrounded by territory of the other, which is in turn surrounded by the first country. There are areas where the nationality of buildings is defined by which street the front door is located on (and where residents have changed nationality by blocking one door and designating a new “front door” - usually for tax advantages).
This is the town of Baarle-Hertog/Baarle-Nassau, a truly fascinating place. Some links (including photos):
http://ontology.buffalo.edu/smith//baarle.htm
http://www.borderlandtv.com/photos_2.html
http://rz-home.de/~mhaertel/baarle2002/index.html
Quibble - the “Kentucky Bend” is not due to a change in the course of the river, but because of a survey error. There’s a common misconception that it was caused by the New Madrid quake, but, in fact, the border was set a few years before the quake. See my response in this thread:
Some percentage of map anomalies are the result of surveyor’s errors. This is probably the reason that Colorado is not QUITE rectangular, but I haven’t been able to confirm it (look at the southern part of Montrose county - you may have to find a good resolution map to see it).
In fact, if you look at a modern map, you will find a place called “Lost Trail Pass” where US 93 crosses the border from Idaho, and where the Continental Divide diverges from the border. Most of the border follows the wrong mountains. At the point where the border shoots straight north to Canada, you will note that they ran smack dab into the Clark Fork river flowing in the “wrong” direction.
Fiddling around with MapPoint, I drew some lines and it appears that the arc has a 12 mile radius:
The arc at the top of Delaware
But when I look at the center, the closest place is New Castle, but it’s still a bit down and to the left.
What’s up with that? Is there anything at the center of the arc, like the surveryer’s grandma’s house or something?
Previous threads about enclaves/exclaves (one old, one not so old):
And an old thread about weird US state borders:
http://boards.straightdope.com/sdmb/showthread.php?threadid=40009
And make sure you take a look at this link:
http://www.ac.wwu.edu/~stephan/48states.html
in the thread about weird state borders.
No one’s discussed it in this thread yet (they have elsewhere), but I’ve always found Maryland’s shape bizarre, even before I came to live here. The state is essentially split in half by the Chesapeake Bay, which in the old days must have been a tiresome obstacle to keep having to cross, when on your way to Baltimore, Washington, or Annapolis from the Eastern Shore. Had I been consulted on the matter, I would have assigned the eastern territory to Delaware.
Not to mention the silly triangular bit up in the northwest (Garrett county), which is connected to the rest of the state by a five-mile wide “isthmus”. What’s with that?
I suspect the history of Maryland’s border is probably dominated the history of settling the Virginia and Pennsylvania borders. Maryland just got squeezed between the two giants.
The center was the dome of the 1732 New Castle courthouse, and the arc was, indeed, specified as a 12 mile radius:
http://www.destatemuseums.org/information/Museums/ncch/nc_courthouse.shtml
That’s neat!
Of course, my own measurements were a bit off – I blame MapPoint.
My own experiments found the center to be in the clearing south east of where the school buses are parked (top center). I’ll trust the original surveyers over MapPoint.
The Gambia was a British colony on the Gambia River surrounded by French-owned territory. When they went to draw the boundary in 1889, they decided that the British territory would be all land that a cruiser in the Gambia River could hit with one of its guns. I don’t think they actually had a ship go out and fire its guns to find out where the border was. Instead they just took the range of a ship’s gun (somewhere around 8 to 10 miles, but I forget the exact distance) and drew the line that far from the river. This gave the country a worm-like shape.
One thing I haven’t been able to find in my reading…
Why did Pennsylvania allow Delaware break away from it? It would seem to me that regardless of what the 3 counties of Delaware wanted, PA would have been better served to keep Delaware under it’s control for direct access to the port potential.
I understand that at the time Philadelphia was a major port, but it’s an inland port, and I would figure that at some point, Delaware would be charging a tax to allow ships to get to Philadelphia up the Delaware river.
Delaware was granted to William Penn. Why did the PA powers-that-were permit Delaware to break away? Did any major dispute occur to try to stop it?
From what I’ve been able to find, it seems like it happened without much pain, but geographically, it certainly didn’t help Pennsylvania’s access to the sea, not to mention losing all of its beachfront property. 
Perhaps it wasn’t an issue in 1704, but clearly someone somewhere might have seen this as not in the best interest of PA. Can anyone fill me in on the rest of the story?
One thing I remember reading a while ago is that Maryland threatened not to join the United States if Virginia, the Carolinas, and Georgia would give up their rights to western expansion. I’m not sure if PA fell into this, as their western border may have been defined. But Virginia was claiming that they had no western boundary. Since Maryland was blocked from western expansion, they realized that their growth in relation to some of the other colonies would be impossible, and over time their influence in the H of R would diminish over time. Virginia, et al agreed to define their western boarders.
