The son of a justice of the Vermont Supreme Court, Isham attended Williams College and the Harvard School of Law before he was admitted to the bar in 1858.

After two years' recovery in South Carolina, Isham returned to Groton, Massachusetts, where he studied at Lawrence Academy.

However, he decided to settle instead in Chicago, Illinois reportedly because he was "favorably impressed with the advantages of all kinds which the city seemed to afford him.

In 1864, Isham was elected to the Illinois House of Representatives as a Republican, where he served a two-year term and was a member of the judiciary committee.

[6] Isham's most notable cases include the arrangement of the Walter Loomis Newberry library endowment and the 1875 mayoral election controversy between Harvey Doolittle Colvin & Monroe Heath.

[7] Fannies first cousin, Mary Weld Burch, was the wife of Alexandre Ribot, the Prime Minister of France.

[7] They had two sons and two daughters, including:[8] Isham was a charter member of the Chicago Club and drafted its incorporation papers in 1869.