I have worked on redoing county boundaries, and it is a tough job with all the relationships to manage. Anyone here willing to take on this task: you have my respect.
Some of the challenges include:
- Unsnapping all the random land use and other elements that people attached to the boundaries, which shouldn’t be there.
- Cutting up the source data—likely imported from elsewhere—at every location where the current county boundary splits due to a municipal boundary, state boundary, river, or some other feature used in the relation.
- For big counties, just getting all the data into JOSM is a chore.
- Dealing with modifying state boundaries as well, especially when the adjacent state boundaries are newer, have a modern source, or are not in alignment with your data.
In my professional experience working for the State of Maryland, I have noticed and pointed out to others that our official state boundary GIS data does not align with the official State of Pennsylvania boundary data. Officially, you will get a response from officials that only the statute can define the state or county boundary. Therefore, it can be open to interpretation as to where the boundary really lies between those two lines. Although OSM is not meant for survey purposes or anything like that, it does end up in a lot of applications where the precise location of boundaries matters to people.