Asa Gray
In 1845, Sprague met Asa Gray (1810–1888) of Harvard College, and, over many years, Sprague illustrated several of Gray’s works, including the plates for the atlas (1857) to "Botany. Phanerogamia" in Charles Wilkes' "United States Exploring Expedition During the Years 1838, 1839, 1840, 1841, 1842" (1845–1876). He also illustrated Asa Gray and John Torrey's various volumes of the U. S. War Department's "Reports..." (1855–1860), as well as works for George B. Emerson, George Goodale, and Alpheus Baker Hervey.