Rarely? Just about every state border in the U.S. has a story like this behind it.
Pennsylvania and Maryland are right next to each other, and it’s not like they didn’t know about each other’s existence. And yet, somehow, they both picked different lines for their border between the two states. Originally, there weren’t many people living in the disputed area, so nobody cared. But over time, more people settled in that area, so you ended up with town that were right next to each other where one claimed to be in Maryland and the other in Pennsylvania. It got so heated that some folks would occasionally do things like grab a bunch of guns and take over the other town’s courthouse until they agreed that they were in the same state.
Pennsylvania and Maryland finally sat down and came to an agreement on the border. There had been so much dispute over the territory that they didn’t trust the local yahoos to survey the new line, so they hired the best experts in astronomy and surveying they could get from Europe, named Charles Mason and Jeremiah Dixon to survey the line. That’s why it is called the Mason-Dixon line.
The town I live in got its charter from Lord Baltimore, and was originally part of Maryland, but is now part of Pennsylvania.
Virginia and Pennsylvania had a similar issue. Pennsylvania claimed their border was a line that went straight west, and Virginia claimed their border was along a river. The problem was that when they finally started exploring the western side of the state, they found that the river turned north and crossed Pennsylvania’s line. Again, for a long time nobody cared, but once the area started getting settled it became a much bigger issue. Both states thought that it would be unfair for either state to get both Wheeling (the biggest gateway heading west at the time) and Fort Pitt (which eventually became Pittsburgh), so they drew a north-south line down the middle, and Virginia got the western side and Pennsylvania got the eastern side. And that’s where West Virginia’s goofy northern panhandle came from.
Then of course there was the dispute between Ohio and Michigan, leading to the Toledo War. Missouri and Iowa had a similar but lesser known dispute over the incorrectly surveyed Sullivan Line.
There are stories like this in just about every state. And not all of these disputes were resolved back in the 1700s and 1800s either. Georgia and Tennessee both currently claim a section of the Tennessee River, so there’s a small section of land there that may end up changing hands at some point. It’s a big issue now because Georgia has been going through droughts in recent years and needs the water access. Tennessee doesn’t want to give up the water, so they aren’t about to let go of their section of the disputed territory without a fight.
As Bijou Drains mentioned upthread, North and South Carolina re-surveyed their border recently and found errors, and some areas ended up changing states as a result. Some people ended up living in a different state as recently as 2017.
A lot of times, once a border marker of some sort has been laid down, both states will accept that marker even though it is later determined that the marker was placed incorrectly. Those old markers aren’t always accepted though, and sometimes the old markers no longer exist or have changed. For example, the border might be a river which moves over time due to erosion and such, or maybe the old markers were things like cut trees which eventually rotted away and disappeared, leaving no trace of where the border actually used to be located.