With all the talk of gerrymandering of late, I was looking up North Carolina's past election maps. And man, the 2016 map which caused the court case looks downright normal compared to some of the ones they've had in the past.

But something caught my eye in the 1993-1998 map. I was under the impression that congressional districts were required to be connected sets, which is why so many districts on that map have narrow corridors connecting them. But I just don't see how districts 1, 3, and 7, or districts 6 and 12, can possibly all be connected.

So I guess I have two related questions

  • Are congressional districts required to be connected? If not, how often have disconnected districts appeared?
  • Are districts in the 1993-1998 map actually disconnected, or is there some geometric wizardry going on at scales that image doesn't resolve?

For this purpose, connection through territorial waters is acceptable, so places like Hawaii or Michigan's upper peninsula that are divided by water don't count.

1993-1998 map

  • Crazy district shapes. Move your leg to the right and jump over three districts kind of shape.
    – Trilarion
    Jul 11 '19 at 21:23

You're talking about contiguity, which refers to the idea that a district is one piece (physically adjacent). A district with a section located in another district – like an island – is not contiguous.

Like the related matters of compactness and preservation of political subdivisions, the issue of contiguity is left to the discretion of each state. The U.S. Constitution and Federal law simply mandate that congressional districts be based on population. Per the Reapportionment Act of 1929, states are allowed to determine the size and shape of congressional districts.

According to the National Conference of State Legislatures (NCSL), it looks like 29 states require contiguous congressional districts, including North Carolina. So I guess there's a road keeping those pieces in your map attached.

  • 3
    But did North Carolina require contiguous districts in 1993, when that map was made?
    – Brythan
    Jul 9 '19 at 18:23
  • 1
    It looks like for NC the contiguous condition was added in 2017, so it wouldn't apply in 1993 for that map.
    – lazarusL
    Jul 9 '19 at 18:28
  • We can actually show that one of either District 1 or District 3 is not contiguous from the map in the question. If we consider just this region we find that there is no way for both to be contiguous. Now, sure, there could be a teeny tiny strip that wraps all the way around the edge in order to connect one or the other, but this is highly unlikely, given that District 1 borders the next state and District 3 borders the ocean, and such a connection would be even more absurd than the gerrymandering visible in District 12. Jul 9 '19 at 21:08
  • @Draco18s Through gerrymandering all things are possible: my city's airport is connected to the city by a 1-foot-wide strip which meanders around the edge of the city in which the airport physically sits.
    – manveti
    Jul 9 '19 at 21:36
  • 1
    @CraigMeier Sure. But as the law at the time of that map didn't require contiguous regions, it's more likely that one or the other is disconnected. Jul 9 '19 at 23:13

This is more of a too-long comment than a specific answer, though the short answer would be that district contiguity is a growing, but not yet universal, trend.

Looking backwards, discontinuous congressional districts aren't the half of it. In the early years of the US, even states weren't necessarily contiguous. For example, what we now call Maine was for several decades part of Massachusetts, with New Hampshire in between. Maine, (after being left virtually defenseless to British invasion and occupation in the War of 1812), grew disgruntled and seceded in 1820. But strategic political redistricting played a significant role:

  • On the state level, Massachusetts' ruling Federalist party didn't want the competition in state politics from the rival Jeffersonian party preferred by Mainers.

  • On a national level, the pending statehood of Missouri as a slave state, (with new congressman and senators), threatened to nudge the balance of power of the US Congress toward the slave states. Maine's statehood restored the status quo.

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