As an interested observer for the last 50 years here in Silverton, I can relate that the original town plat of the town dating from 1874 is very accurate and still forms the basis of the survey the town uses. There have been several annexations including some recent ones. I noted one of the maps shows the Melville Monument and that is still the U.S. mineral survey monument used by surveyors as well as one on the opposite side of town. The only era when I can note any lack of attention to the use of land, not the surveys, was perhaps in the 1940s and 50s. When people start waving their hands about where things are located, a survey settles the question. Our county surveyor is a U.S. Mineral Surveyor which is fairly rare in this country. The railroad maps are very accurate and form the basis of today's land ownership by the D&S. They still pay property taxes on the 20 acre parcel shown on the maps as Station Grounds that are adjacent to the town boundary. And the D&S is by far the largest land owner in the town. When it comes to land ownership in the county, the railroad operates by easement over land owned by the federal government. All my land in both the town and county except a lot in Eureka has been surveyed and it all ties into the existing surveys.
The interesting question has been Gladstone. The typography has been changed so radically by mining from the Sunnyside Mine and now the EPA Superfund Site but the property lines haven't changed much from the early 1900s. Throw in the railroad right-of-way which was conveyed to the county upon abandonment and it was quite a mess to figure out. But that's a whole different story.