Clifton was a minor criminal wanted in the Oklahoma Territory for robbery, safecracking, and cattle rustling before joining the Doolin Gang in 1892.
Following the gang's escape, and eventual disbandment, a bounty of $3,500 was placed on Clifton, who was becoming popularly known as the "most killed outlaw in America", as people would repeatedly turn in a corpse claiming the body as Clifton's, despite the fact the bodies had all 10 fingers, while others, who would randomly cut off three fingers, would often cut the wrong ones.
While the man in question was missing the correct fingers, the outlaw killed was suspected to have actually been Buck McGregg.
A character named after Clifton appears in the 1997 Western-themed first-person shooter Outlaws by LucasArts.
[1] The historical Clifton was also a known safecracker as well as a thief and cattle rustler who ran with Bill Doolin's gang.