I don't know when it reached the South, but some of the first albums I can remember hitting here and hitting big were:

Eric B. and Rakim: Paid In Full (87 or 88)
NWA: Straight Outta Compton (88)
Eazy E: Eazy Duz It (88)
Cypress Hill: Cypress Hill (91)

Then the South got real heavy once we had our own in it:

Geto Boys: The Geto Boys (90)
UGK: Too Hard To Swallow (92), Super Tight (93)
Outkast: I'm not typing the whole album name (94)

But that Eric B. and Rakim and NWA was the first rap songs I can really remember off the top of my head right now as being the "first". I'm sure there are some I'm forgetting. While The Geto Boys had my attention, none of them hit me as hard as Super Tight did by UGK. They put the South on the map in terms of mainstream and I remember EVERYBODY was wanting to borrow Super Tight as it was really the first CD I ever bought. All the others were on bootleg cassette tape.