> pre-1870, where Germany was divided into 39 independent states

The 39 independent states is only correct for a few years in the 19th century. Summarizing the changes in number of states of the German confederation since 1815:

  1815: 39 (German Confederation founded)
  1817: 40 (Hesse-Homburg admitted)
  1839: 41 (Limburg added)
  1850: 39 (Prussia annexes two Hohenzollern duchies)
  1853: 38 (Anhalt-Köthen merged)
  1863: 37 (Anhalt-Bernburg merged)
  1866: 36 (Confederation collapses; Prussia absorbs Hanover etc.)
  1867: 26 (22 in North Confederation + 4 southern kingdoms)
  1871: German Empire formed, states are no longer independent