Joseph George Rosengarten (July 14, 1835 – January 14, 1921) was a Philadelphia lawyer, historian, and Civil War veteran. He witnessed John Brown's raid on Harper's Ferry and served on the staff of General John F. Reynolds. An amateur historian, Rosengarten was particularly interested in the subject of French and German immigration to the United States, and the role played by French and German immigrants in the foundation of the country. He authored numerous articles on the subject and two books: The German Soldier in the Wars of the United States andFrench Colonists and Exiles in the United States.
Few men had such a large circle of acquaintance; and having a rare gift for friendship, he continued to maintain association with many of those with whom he was thrown into contact either in Philadelphia or through his frequent trips abroad. He knew the Darwins, father and son; he came into close touch with eminent writers and scholars like F. Max Müller, Thomas Hughes, Goldwin Smith, Herbert Spencer, and Lord Bryce; he formed a friendship extending over many years with the de Rochambeau family and secured the passage of an act of Congress for the purchase of the letters of Washington to the Comte de Rochambeau. He knew the great trio of American literature, Longfellow, Emerson, and Lowell; he had met all the Presidents from Buchanan to Wilson, and knew practically all the generals in the Civil War.
Rosengarten was also involved in numerous philanthropic pursuits. He is buried at Laurel Hill Cemetery in Philadelphia.