Phelps was Envoy to Court of St. James's in Britain from 1885 to 1889, and in 1893 served as senior counsel for the United States before the international tribunal at Paris to settle the Bering Sea Controversy.
In politics, Phelps was always conservative, opposing the anti-slavery movement before 1860, the free-silver movement in 1896, when he supported the Republican presidential ticket, and after 1898 becoming an ardent "anti-expansionist." .