There were several families in the Judengasse with the name Speyer, but most of them were not related. The largest and most prominent was the family of Michael von Speyer, who migrated to Frankfurt in 1644 from the city of Speyer. This family was one of the great Frankfurt Jewish families right through to the 20th century. The founder Michael held the office of community leader. His descendants quickly acquired great wealth through money changing and lending and by supplying the imperial army. Isaak Michael Speyer, who lived in the 18th century, amassed the largest fortune ever for a Frankfurt Jew by 1800. Individual family members emigrated to America in the 19th century, where they became successful bankers. One member of the American branch revived commercial links with Frankfurt in the 1980s as one of the financiers of the Messeturm, one of the tallest office buildings in Europe. The main Frankfurt branch of the Speyer family died out: its last major representative was the banker Georg Speyer (1835 1902), who left his large estate to a number of foundations with social and scientific aims, including particularly Frankfurt university and the Georg-Speyer.-Haus, an important medical research centre.