Willie Dixon arguably the "Father of Slap Bass" has a recording of his trio from the late 1940's that was very influential to me and many other slap bass players - (including Lee Rocker of the Stray Cats). Here is a video of Willie Dixon from later in his Career.
At one time Willie lived in the Denver CO area. I never met him, but I did meet his Son who approached me at a gig and said "My Father used to play like that". The Son was surprised when I said Willie was one of my main influences.