which political group did he join during 1931?
Nazi Party
Albert Speer
In January 1931, Speer applied for Nazi Party membership, and on March 1, 1931, he became member number 474,481. 
who is albert speer? The Minister of Armaments and War Production when was he born? March 19, 1905 where was he born? Mannheim
wiki:1596230
Albert Speer [SEP] Joining the Nazis (1931–1934)
In January 1931, Speer applied for Nazi Party membership, and on March 1, 1931, he became member number 474,481. The same year, with stipends shrinking amid the Depression, Speer surrendered his position as Tessenow's assistant and moved to Mannheim, hoping to make a living as an architect. After he failed to do so, his father gave him a part-time job as manager of his properties. In July 1932, the Speers visited Berlin to help out the Party before the "Reichstag" elections. While they were there his friend, Nazi Party official Karl Hanke recommended the young architect to Joseph Goebbels to help renovate the Party's Berlin headquarters.