Nope....they have been found here in the north too. But it is a lot more rare.
And Black Widows and Brown Recluse aren't the only bad bites to have. My son was bitten by a normal spider (not a BR or BW) on the inside knee just above his calf a few months ago...and the bite went into sepsis. His whole leg was almost double in size before they got it under control. I only saw the pictures, but it was VERY nasty looking.
He has always been petrified by spiders. (probably learned from me, only he is worse) I'll bet he is doubly so now.