Chorpenning was born in Somerset County, Pennsylvania, the son of a county judge. He spent his youth in Somerset, and as a young adult he established a business in nearby Stoystown, Pennsylvania. In 1850 he traveled to California in search of gold. Although he did not become wealthy by mining, he could see the critical need for fast and reliable mail service between California and the eastern states, most of which was then being transported by sea around South America.