I've started collecting, photographically and geospatially, Kent/Sussex Boundary Monuments. These are stone monuments, set in the past to mark parts of the boundary between the two counties. Most of the boundary follows streams, but there are two stretches of lines which run from point to point. Most of those points are marked with stone monuments. The New Castle/Kent boundary is similar.
Staff from all three Delaware counties and several state agencies have started a project to improve the accuracy of the geospatial data that we use to represent the county boundaries in our GIS tools. We have been looking at historic surveys and have noticed references to stones that serve as monuments in several places. So I have started do some scouting to see if we can find these. And, of course, I take pictures.