The Senate Momper' held office from March 16, 1989, to January 24, 1991, initially as the government of West Berlin and, after German reunification on October 3, 1990, together with the East Berlin Magistrat Schwierzina as the government of the new Land Berlin. After the surprising election victory in the Election to the House of Representatives on January 29, 1989, the red-green coalition between the Berlin Social Democratic Party (SPD) and the Alternative List for Democracy and Environmental Protection (AL) replaced the previous CDU/FDP government under Eberhard Diepgen. Governing Mayor became Walter Momper (SPD). The SPD/AL alliance was the second red-green state government in Germany after the 3rd Börner government in Hesse (1985 to 1987).
The fall of the Berlin Wall marked a turning point both for Berlin and in the twenty-month term of office of the Senate. After the reunification of Germany and Berlin, Senate Momper held office for more than three months together with Magistrate Schwierzina as the government of Berlin as a whole. After ongoing conflicts, the AL left the coalition on November 15, 1990, two weeks before new elections to the House of Representatives were scheduled anyway. The reason for this was the battle of Mainzer Straße initiated by Erich Pätzold (SPD). In the first all-Berlin election to the House of Representatives on December 2, 1990, both the SPD and the AL suffered heavy losses.