Born in Willstätt, he emigrated to England in 1773 and later to the colony of New York where he became a merchant.
Being a Loyalist, he left America after the American War of Independence and returned to England.
Through endeavours that started with his first grocery store and extended to real estate operations, with money lending and discounting in between, Pozer succeeded in building a fortune over 30 years.
After this unsuccessful attempt to settle German compatriots in Aubert-Gallion, Pozer, despite being a Protestant and a Loyalist, began collaborating with the Catholic Church and the francophone population.
He gave the land to the Archdiocese of Quebec for the establishment of the parish of Saint-Georges.