How did Prussia gain power in the 19th century?

Throughout the 19th century, Prussia became much more prosperous, her military improved immensely and education improved greatly, promoting Prussian nationalism greatly. How? One answer: industrialisation and economic development.

During the Congress of Vienna, Prussia got the Rhineland from France, an extremely industrial area. However, the Rhineland was not attached to Prussia and there were several states in between the two. Also, the population of the Rhineland looked down on the Prussian agricultural society and felt that they would be better off if they were independent. 

In 1818, some Rhinelanders complained to the King of Prussia about the many tariffs and customs barriers placed on goods going from the Rhineland to Prussia, through multiple states. Moreover, the different currencies throughout each state made it difficult and rather inconvenient to trade. In the same year, the Prussian   government formed the Prussian customs union. This reduced the tariffs for goods going out from the Rhineland to go to Prussia and vice versa and they were all payed at once. This was called, as well as the Prussian Customs Union, the Zolverein.

Some north and central Germanic states were impressed by Prussian's economic pressure or forced by economic downfall, joined the Zollverein, and in 1828, Hesse-Darmstadt was persuaded to join, establishing a trade route south of the river Main. 

Nevertheless, some other states were stubborn and refused to join, such as Hesse-Cassel and Hanover. Instead, they formed the Middle German Customs Union ( Hanover, Brunswick, Saxony and several smaller states ) and another, consisting mainly of Bavaria and Württemberg. 

In 1830, Hesse-Cassel, a small but vitally important state of the middle customs union, ran into financial difficulties and revolutionary upheavals. The following year, to the horror of its fellow Middle Customs Union states, it joined the Zollverein. In 1834, Bavaria and Württemberg joined, the Zollverein now including 18 states and 23 million people, and in 1836, the both important states Bade
n and Frankfurt joined, the Union being then formed of 25 states. This Customs Union was, as one can suspect, extremely successful and gave Prussia extremely tactical control of the Germanic states. The Zollverein Congress achieved multiple things: it unified the states into one currency (the Mark) and unified the units of measurements in all of these states. Additionally, huge progress was made on the railway network, which trade benefited from hugely. 

Why go through all this detail? 

Well, this Zollverein Union would later be the key of German Unification. Austria refused to join it in the beginning and when later it asked to, the Prussians simply said that they had not been willing to take the risk originally, so why should they benefit from it? (Which is fair enough, in my opinion) 

The economic power of Prussia gave it a massive influence and of course, a state with economic power also has political power. Furthermore, the developing of the Prussian economy, as previously mentioned, aided its education, military and it's society in general, which would, in 1866 help it win the Austro-Prussian war and helped it become an important European nation. 

Map of German Confederation in 1815