Many of Seward's speeches and written works, as well as secondary sources written about Seward, have been digitized and housed in the Internet Archive Digital Library. You can find them by searching under his full name.
Bigelow, John, UC 1835, and Hon. UC 1868. Retrospections of an Active Life. New York: The Baker & Taylor Co, 1909. E469.B59 1909 v. 1-3 (Special Collections).
John Bigelow Papers 1820-1872 (Consult the name index) For more information on the papers or if you are searching for a specific individual in the papers, visit the index to the papers.
Seward, William H. Alaska Speech. Alaska, Sitka. 12 Aug. 1869. Internet Archive. Web.
Barry, Mary J. Seward, Alaska: A History of the Gateway City. Anchorage, Alaska: M.J.P. Barry, 1986. Print.
Hallock, Charles. Our New Alaska: Or, the Seward Purchase Vindicated, Forest and Stream Publishing Co., New York, 1886. Print.
William Henry Seward was born in Florida, Orange County, New York in 1801. He graduated from Union College in 1820 and soon became a senator for New York in 1830, with the backing of Thurlow Weed. After Abraham Lincoln's election, Seward was appointed as the US Secretary of State, a position he held until 1869.
During the Civil War, Seward dealt with the major issue of European intervention, especially the possibility of France and Britain supporting the Confederacy. Perhaps Seward is most known for arranging for the purchase of Alaska in 1867. Seward was seriously wounded during the Lincoln assassination and retired from public office in 1869, He died on October 10, 1872.
Lothrop, Thornton Kirkland. William Henry Seward. New York: Houghton Mifflin and Company, 1896.
**This text is also available electronically at: https://archive.org/details/williamhenrysewa00lcloth
Taylor, John M. William Henry Seward: Lincoln's Right Hand. Washington, D.C.: Brassey's, 1996.
"Great Union Names Part I: William H. Seward." Union College Magazine. Summer 2001. (Available in periodicals in the basement).
There are quite a few databases available through Schaffer Library that hold articles dealing with William Henry Seward, especially on the topic of his political career. You can also search through all of the databases as well as the catalog using Primo.