Top fermented yeast works at temperatures between 16 and 20 degrees clecius, basically room temperature, while bottom fermented yeast needs temperatures around 4 til 9 degrees clecius. Obviously, before refrigeration the regional climate would play a role in which beer was typically brewed. Due to the cooler climate in the south of Germany, bottom fremented lagers were typical, while in the north warmer climates prevailed and so did the top fremented beers. Additionally, the use of ice to keep the temperature of fermentation cellars low in former times aided in the ability to brew bottom fermented beers. Of course, ice is more easily accessable in the southern states like Bavaria and Baden-W�rtenburg which are close to the alps than in the warmer northern german states.
Bottom fermented beer was already being brewed since the 1500's in Bavaria, and the most famous bottom fermented beer, the Pilsner (or Pils) was first brewed in Bohemian city of Pilsen in 1842. Even though the first pilsner was brewed in the Czeck Republic it was made by a german brewmaster who travelled there for the high qualtiy water and hops. The bavarians didn't care too much for this beer (and today still prefer thier helles over a pilsner) however, at the time people in Berlin highly favored this beer.