Humphrey's father gave up the tannery business after several years and began to practice law.

He participated in twenty-seven battles and skirmishes including Fort Donelson, Shiloh, Corinth, the siege of Vicksburg, Resaca, and Atlanta.

Short on funds, Humphrey left school, but was admitted to the Ohio bar in 1868.

He gave up the newspaper a year later and settled into the practice of law full-time, until December 1872 when he helped found the Commercial Bank of Independence.

Humphrey was a devoted Republican and was active in party politics in every state in which he lived.

In 1872 he unsuccessfully ran for the Kansas House of Representatives because he opposed the issue of railroad bonds.

Before his term expired, Humphrey was appointed the ninth lieutenant governor to fill the vacancy left by Melville J. Salter.