who were the first artist or artists to record a successful rap song?

Answer 1

1979 earliest I could find:

"The Sugarhill Gang releases 'Rapper's Delight.' Built on a sample of Chic's disco hit 'Good Times' and written by Grandmaster Caz of the Cold Crush Brothers, it goes on to become hip-hop's first hit and mainstream America's first exposure to rap music."

Answer 2

"Out of Sight" recorded in 1964 by James Brown is considered the first rap song by some music experts.