A Union Army veteran of the American Civil War, he was an early white settler of Wyoming, and served as its treasurer, auditor, and delegate to Congress.

After statehood, Downey continued to serve in local and state office, including Speaker of the Wyoming House of Representatives.

[2] On 31 October 1861, Downey enlisted in the Union Army for the American Civil War, joining 3rd Maryland Infantry Regiment, Potomac Home Brigade as a private.

[3] Near Boonsboro, Maryland, Downey's patrol encountered Confederate commander Stonewall Jackson and his staff riding in advance of their troops on the Sharpsburg Road.

[4] During his congressional term, Downey earned nationwide headlines after he proposed legislation that would have declared the United States to be "a Christian people" and appropriated $500,000 (about $14.5 million in 2022) to create and install Christian-themed paintings and other artwork in federal buildings.

[5] Press coverage of Downey's unsuccessful bill began after he obtained permission to have printed in the record his remarks in favor of his proposed law, which was revealed to be a 15 page prose poem, Argument of Hon.

[4] Downey had two daughters with his first wife, Fannie Fisher who died in 1870, not long after the family moved to Laramie, Wyoming.

His daughter, Dr. June Etta Downey (1875–1932), became a prominent psychologist, and a professor of psychology and philosophy at the University of Wyoming.