Joseph George Rosengarten was born in
Philadelphia, Pennsylvania, the child of German immigrants George D. and Elizabeth (Bennett) Rosengarten. His father, one of Philadelphia's wealthiest men by the 1890s, was an accountant and manufacturer, who created a large chemical establishment and had an interest in numerous other profitable business ventures, including the
Pennsylvania Railroad. Rosengarten received his early education in private schools in Philadelphia, and for a time came under the influence of a scholarly man in
York, Pennsylvania, the Rev. Charles West Thomson, who aroused in him a liking for literature that became "an abiding habit." He completed his secondary education at an academy then affiliated with the
University of Pennsylvania, studying under Dr. Samuel Crawford. In 1849, at just fourteen years of age, Rosengarten was admitted to the
University of Pennsylvania, graduating three years later with the degree of
A.B. in the Class of 1852. In 1855, Rosengarten received the degree of
M.A. from the same university. After graduation he studied law in the offices of Henry M. Phillips, a prominent member of the
Philadelphia Bar, and in 1856, Rosengarten was admitted to practice. Rosengarten's father then arranged for him to travel abroad to further his studies: The elder Rosengarten, realizing the extraordinary value of foreign study and travel, sent four of his sons abroad to prepare themselves for their future careers. In pursuance of this plan Joseph Rosengarten went...to study history and Roman Law at the
University of Heidelberg and to engage in travel. While abroad he was "thrown into contact with men of distinction," including
Ludwig Häusser and
:de:Adolph von Vangerow, who served respectively as professors of history and law at the University of Heidelberg. During this period, Rosengarten also met the eminent
British jurist James Fitzjames Stephen, and his brother, author and critic
Leslie Stephen. In 1857, Rosengarten returned to the
United States and began practicing law in Philadelphia. His law partners were
Henry Schell Hagert and George Junkin. ==Witnesses John Brown's raid on Harpers Ferry==