Ches Whitley
Ches Whitley was a Human male living in the late 19th century.
Whitley was an acquaintance of Samuel Clemens and an employee in the County Assayer's Office in San Francisco on Earth in 1893. He informed Clemens that Data had visited his office several times, seeking information on mining operations in the 1850s, and asked Clemens to say hello and inquire when Data was coming back. Data hadn't known his name and had spoken to several employees there. (TNG: "Time's Arrow, Part II")
This character was only mentioned in dialogue.