Born in Sandusky, Ohio, in 1825, a son of Congressman Eleutheros Cooke, Henry D. Cooke studied at Allegheny College in Meadville, Pennsylvania, and Transylvania University in Lexington, Kentucky, where he graduated in 1844. He began to study law but soon turned his attention to journalism. In 1847, he sailed for Valparaiso, Chile, as an attaché to the United States consul there, but was shipwrecked. He was detained after the wreck at St. Thomas, where he conceived the idea of a steamship line from New York to San Francisco via the isthmus of Panama and wrote about his idea to the Philadelphia "United States Gazette" and the New York "Courier and Enquirer". Consul W. G. Moorhead told other State Department officials about the idea, and in about two years the Pacific Mail Steamship Company was organized. Cooke afterward lived in San Francisco, where he was connected with shipping interests. He was the first to announce to the authorities at Washington, through a despatch from the military governor of California, the discovery of gold in the Sacramento valley. Becoming involved by suretyship for a reckless speculator, he lost his fortune. (Another source says a fire in San Francisco left him burdened with debts.)