John Hipple Mitchell was born in 1835 in Washington County, Pennsylvania, with the name John Mitchell Hipple, and changed his name when he came to Oregon in 1860. The Oregonian newspaper would later allege that he had made the name change when he abandoned his first wife, Sarah Hoon, and fled Pennsylvania with his mistress.

Mitchell became city attorney of Portland, Oregon, in 1861, and in 1862 was elected to the Oregon Senate; during this time, he also had a private law practice. In 1873, he successfully challenged Henry W. Corbett for Corbett's seat in the U.S. Senate. He lost reelection in 1878, but returned to the Senate in 1885. In 1896, a political coalition led by Henry W. Corbett, Jonathan Bourne, and William U'Ren successfully blocked Mitchell's reelection by preventing a quorum in the Oregon legislature for its entire 40-day session. The legislature did not appoint a new senator until a special session in 1898, when it elected Joseph Simon. After his 1896 defeat, Mitchell returned to private practice, before he made a comeback and won a fourth term in the U.S. Senate in 1901. During his career in the Senate, Mitchell was successful in gaining federal appropriations for Oregon, such as funding for a U.S. government exhibit at the Lewis and Clark Centennial Exposition.

Mitchell married Sadie Hoon in 1857; the couple had two children. In 1862, Mitchell remarried to Mattie Price, and they had six children.

On December 31, 1904, a federal grand jury indicted Mitchell on the charge that he had accepted bribes in exchange for influencing the General Land Office to approve fraudulent homestead patents that were then sold to lumber and livestock companies for a profit. Although Mitchell denied the charges, both his law partner and his private secretary testified against him. Mitchell was convicted in 1905. That December, Mitchell died from complications of dental surgery, while awaiting his appeal to the U.S. Supreme Court.

Sources: John Hipple Mitchell (1835-1905), by Oliver Tatom, Oregon Encyclopedia, https://www.oregonencyclopedia.org/articles/mitchell_john_hipple_1835_1905_/#.Yz4BPHbMIuV; "Oregon Land Fraud Trials (1904-1910)," by Oliver Tatom, Oregon Encyclopedia, https://www.oregonencyclopedia.org/articles/oregon_land_fraud_trials_1904_1910_/#.Yz3_fHbMIuU; "Dictionary of Oregon History," second edition, 1989, edited by Howard McKinley Corning.