[2] After returning to New York, Hague was selected by financier William H. Webb to explore several equatorial coral islands in the Pacific Ocean.

Webb was involved in the guano business, and Hague examined and documented phosphate deposits on Baker, Howland, and Jarvis Islands.

[3] During the American Civil War, he spent 1862 and 1863 in Port Royal, South Carolina, as a judge advocate for the U.S. Navy, handling negotiations involving the Atlantic Blockading Squadron.

He then worked for Edwin J. Hulbert, developing the Calumet and Hecla copper mines in Michigan, before joining Clarence King in 1867 as an assistant geologist on the Geological Exploration of the Fortieth Parallel.

[2] In 1887, Hague acquired the North Star Mining Co. on Lafayette Hill near Grass Valley, California, which he had helped develop during his time in the state.