I hope, that the distinction "east/west" will be over soon. Non locals ask me: "are you an Ossi ( east-) or a Wessi (west-citizen)?"

...My answer is: Ich bin ein Berliner !    ©  by: J.F.K.. June 27th 1963

... after the reunion Berlin was arranged in 23 boroughs ...later Berlin became arranged in 12 boroughs...

partial former east and west boroughs were united in area and names.

(Hohenschönhausen, Weissensee, Wedding, Tiergarten, Prenzlauer Berg and Pankow lost their own names.)

Wedding, Tiergarten (west.) and Mitte (east.) merged to MITTE,

Hohenschönhausen, Weissensee, and Pankow merged to Pankow

only Reinickendorf, Spandau and Neukölln stayed and the other: 

Charlottenburg-Wilmersdorf,       Zehlendorf-Steglitz,      Marzahn-Hellersdorf, Schöneberg-Tempelhof,   Hohenschönhausen-Lichtenberg,   Friedrichshain-Kreuzberg und Treptow-Köpenick

merged and have a double name. 

Since 1945 untill 1989 Berlin was dividet in 4 part under allied government USA, Great Britain, La France and Soviet Union. 

It was a result of the WW II.

for all who like it, here is the former BERLIN under Allied Government...