Since they were part of slave trade, musicologists see early banjo-like instruments made of gourds primarily as early as the 17th century.
The first white man to popularize the banjo was "Sweeney" in 1830.
Tenor banjos became popular in Irish music in 1962 with the Dubliners re-tuning the instrument in from a C,G,D,A tuning (like a viola, cello), to a G,D,A,E tuning (like a violin) for ease of playing by fiddlers.
Tenor banjos were also used in the early 1900s in New Orleans Jazz Bands and later Dixieland bands for their volume and chordal capabilities.
Today, tenor banjos are still quite popular in Irish music and you won't see a seisun without one!