Enlisted as a private in Company E, 12th Regiment, Illinois Volunteer Infantry, June 13, 1861.

After his military service, he enrolled in the law department of Harvard University, graduating in 1868.

In 1904, Warner ran for Governor of Illinois as a Republican, but he failed to win his party's nomination.

After the election, President Theodore Roosevelt nominated Warner for the job of United States Commissioner of Pensions, heading an agency within the Department of the Interior which was roughly equivalent to today's Department of Veterans Affairs.

When Moore died in 1901, he left his collection of books to the city of Clinton, provided a proper library could be constructed to house it.