The construction of the Berlin Wall along this frontier in 1961 led to the section of the U1 that traversed the  into East Berlin being abandoned, and the remainder of the line instead terminating prematurely at Schlesisches Tor, the last station within West Berlin.
The construction of the Berlin Wall in 1961 along this frontier resulted in the U1's section crossing into East Berlin being abandoned, and the remaining portion terminating prematurely at Schlesisches Tor, the last station within West Berlin.