After moving to Hartford, Phelps began manufacturing saddles and shipping them to the South. His business grew rapidly. He had a large brick building constructed on North Main street, which became known as the "Phelps Block." In 1812 he moved to New York City and began doing business with Elisha Peck under the firm name of Phelps, Peck & Co. in the United States. In Liverpool, England, where Peck managed it, the firm was known as Peck, Phelps & Co. They dealt in metal imports from England including tin, tin plate, iron, and brass; and exported cotton from the South to the textile mills in England. Such cotton trade was highly important to England and contributed to its considering support for the Confederacy during the American Civil War.