German customs

The original customs union, or Zollverein, was established by Prussia along with 17 other states which make up modern Germany in 1834. Prior to that, traders crossing what is now Germany, were obliged to make multiple declarations and pay taxes as they moved across state borders.
— It had taken 15 years to establish, but achieved a big step towards realisation in 1828 when Prussia formed a union with neighbouring state Hesse-Darmstadt, Bavaria formed its own union with Wurttemberg, and Saxony with Thuringian.