Born into a poor family in Massachusetts, Peabody went into business in dry goods and later into banking. In 1837 he moved to London (which was then the capital of world finance) where he became the most noted American banker and helped to establish the young country's international credit. Having no son of his own to whom he could pass on his business, Peabody took on Junius Spencer Morgan as a partner in 1854 and their joint business would go on to become J.P. Morgan & Co. after Peabody's 1864 retirement.