Born in the Prussian town of Langendorf (Upper Silesia), Michael Gratz and his five siblings were orphaned when their father, Solomon Gratz, died before his time. Michael and his brother Barnard lived in the household of their oldest brother, Hayim, until they were of age to leave home and seek their fortunes. Michael, in particular, would see a significant portion of the world before he joined Barnard in Philadelphia. The restless younger brother in a family of ambitious merchants, Michael had gone first to Berlin to try to make it in business. When that attempt failed, he found himself in Amsterdam, and then London. He next sailed off for the English trading posts in India but returned again without having met success. All of this took place by the time he had turned 18.

Concern for his brother’s future led Barnard to invite Michael to join him in Philadelphia in 1758. Michael, now 18, quickly accepted the proposal. Barnard was able to set him up in a position working under David Franks, while Barnard pursued business under his own name. Less than a year later, Michael began some small ventures in trade both with Barnard and independently. By 1765, he had left the Franks firm and joined Barnard full time. The firm of B. & M. Gratz was now in full swing, and together the brothers engaged in a variety of trading activities, from Indian trade and land speculation to the coastal trade with the Caribbean. Among their more important business connections was Joseph Simon, an Indian trader established in Lancaster, to the west of Philadelphia. Simon, a devoutly observant Jew, was on the lookout for potential husbands for his six daughters who met both his exacting religious standards and his need for business partners. Although at first he disliked Michael, Simon was eventually won over. His eldest daughter, Miriam, then 20, wed the 29-year-old Gratz in 1769.

Michael and Miriam would have twelve children, of whom only one died young, sparking the predominance of the Gratz family in Philadelphia’s Jewish circles. Michael’s business instincts were successful over the course of many years, and his family enjoyed the benefits that wealth and standing brought. Among their children were Frances, Rebecca, Benjamin, Rachel, Hyman, and Joseph. All of the children received secondary level education, and Michael was able to provide college education for several of them. However, his mercantile career was cut short when he suffered a debilitating stroke in 1800, when he was 62. He would linger for another eleven years and finally died in 1811, surviving his much-lamented wife by three years.