So, the census needs maps (and best we are able to double check that, as it is used to apportion representatives). But also: the modern nation-state is, in many

So, the census needs maps (and best we are able to double check that, as it is used to apportion representatives). But also: the modern nation-state is, in many ways, founded on the notion of maps. A nation exists not just by itself but instead of and in place of other government. So it's pretty reasonable to assume public maps come from a time where e.g. the western border of the country was fuzzy and who controlled what was information of great importance. For instance, if it's 1823 and I'm looking to farmstead, a map both legitimizes, in some way, American rule, and delineates reality about Comanche raids (which were not something you'd want to bump into). I generally like open government, but I think this particular practice may come from a history where maps were more interesting and relevant to the integrity of the nation-state.