Murphy was elected alderman in 1860.
He served as delegate to the Democratic National Convention in 1864 and 1868.
In 1867, he moved to Davenport, Iowa and continued the practice of law.
Murphy was elected mayor of Davenport in 1873 and again in 1878.
He served one term as a member of the Iowa Senate from 1874 to 1878.
He was an unsuccessful candidate for election in 1876 to represent Iowa's 2nd congressional district in the Forty-fifth Congress.
In 1882, Murphy again ran for Congress, challenging a freshman incumbent Republican, Sewall S. Farwell. After Murphy won the general election, he took his seat in the 48th United States Congress.
Grave in Mount Calvary Cemetery
Then, after winning re-election two years later (in 1884), he served in the 49th United States Congress. However, when seeking a third term in 1886, Murphy was defeated in the Democratic district convention, by Walter I. Hayes. In all, Murphy served in Congress from March 4, 1883 to March 3, 1887. Between the Civil War and the Great Depression, Murphy and Hayes were the only two Democratic congressmen from Iowa to serve two or more full terms.
He lived in retirement in Washington, D.C., until his death in that city on December 11, 1893.[1] He was interred in St. Marguerite's Cemetery (now Mount Calvary Cemetery) in Davenport.