I know there have been several threads on this before but maybe time for a rehash? In my reading of past threads there seems to be a mild consensus that Rocket 88 (Ike Turner/Jackie Brenston, 1951) was the first, and indeed throughout the internet.
But I’d like to make the case for Goree Carter’s Rock Awhile (1949). It has the similar R&R feel to it with the big (IMHO) advantage of having a strong rock guitar sound which 88 doesn’t have. And it was recorded a good 2 years earlier.
The guitar has a very Chuck Berry feel despite having been recorded 6 years (!) before Johnny B. Goode (the opening riff of JBG having been lifted from Louis Jordan’s Ain`t That Just Like A Woman (1946).
If you want to look at the country part of the rock and roll equation, there’s 1947’s Move It on Over by Hank Williams. I dare you to isolate Zeke Turner’s guitar and tell me it isn’t rock and roll.