Although Gardner was only involved with the group for a short period of time, he would be prominently mentioned in Ness's memoir of the investigation, The Untouchables, and inspire a recurring character in the 1959 television series based upon that book.

Gardner enlisted in the United States Army as a private during World War I and became the only "Indian" to receive a captain's commission at Fort Sheridan.

The Gardner family traveled all over the United States, from Maryland to Texas, primarily because of Bill's highly mobile professional lifestyle, involved in both law and athletics.

Two years later, he served alongside Eliot Ness on a squad of special agents sent to Chicago with orders to combat the rampant bootlegging and lawlessness caused by Prohibition.

[1]: 121–125, 319–321 In late 1930, Ness was chosen to lead a smaller, select unit of Prohibition agents specifically ordered to investigate the bootlegging operations of the Chicago Outfit run by Al Capone.

[1]: 311–314, 317–329, 360–365 Less than two months after joining the squad, Gardner absented himself from duty without official leave, then abruptly returned only to resign from the bureau three weeks later.

Although Gardner did participate in the early stages of the Untouchables' investigation, he took no part in the high-profile raids that would make Ness's unit famous.

[1]: 329 [3]: 16, 98–99  He also inspired Michael Horse's character, George Steelman, Native American agent under Tom Amandes's Ness, in the revived series syndicated to local stations in 1993.