The banjitar has been around for more than a century, but Johnny St. Cyr holds the historical place of being the first person to be recorded playing one. Here is a great article about him.
St. Cyr also played guitar and tenor banjo, but he often played banjitar with Louis Armstrong's band. The extended range often allowed him to comp bass lines in the absence of a bass player. Video below shows him in the background. I love how fluid his playing is and how natural he is at voice leading when doing chords.