Joseph Medill was born in Saint John, Canada, on 6th April, 1823. He moved to the United States and began working for newspapers in Ohio (1849-51) and Cleveland (1851-55).
A founder member of the Republican Party, Medill moved to Chicago where he joined with Charles Ray to purchase the Chicago Tribune in 1855. A strong opponent of slavery, Medill supported Abraham Lincoln in the 1860 presidential election.
A member of the group known as the Radical Republicans, Medill strongly criticised Lincoln's decision to appoint conservatives such as Simon Cameron (Secretary of War), Gideon Welles (Secretary of the Navy), Edward Bates (Attorney General), and Montgomery Blair (Postmaster General) to the Cabinet. He urged the formation of black regiments and in one editorial Medill accused Lincoln of following policies idesigned to "placate a few hundred Kentucky slave masters".
Medill failed to persuade Abraham Lincoln to appoint Benjamin Butler as his Secretary of War. However, he refused to support other Radical Republicans who wanted John C. Fremont or Salmon Chase as the Republican Party candidate in the 1864 presidential election. Instead he urged his readers to remain loyal to Lincoln's candidacy.
In November, 1871, Medill was elected mayor of Chicago. While in power he helped establish the Chicago Public Library.
Joseph Medill died in San Antonio, Texas, on 16th March, 1899.