You'll pick up a lot of post-WWII differences, but you can still try. There's an interesting paper exploiting the meandering of river-defined national borders t

You'll pick up a lot of post-WWII differences, but you can still try. There's an interesting paper exploiting the meandering of river-defined national borders to do a discontinuity design for long-run effects of the Austro-Hungarian Empire, for example, which is at least not obviously wrong.