Williamson Bros is a big barbecue outfit in the suburbs of Atlanta. Alabama natives Danny and Larry Williamson opened the first location in 1990, and it has since become a Cobb County institution. I have never been to the restaurant, but I'm happy to give their sauce a go.
This sauce is an attractive bright red, but it's far from the consistency of ketchup. It's thinner than most that you find in the grocery store - not too much thicker than water. It's got a lot of bits of stuff suspended throughout - some bits of onion, but mostly spices. The sauce is immediately sweeter than you'd expect such a thin sauce to be, but the vinegar definitely makes its presence felt, too. It packs a pretty potent peppery punch, but won't light you up by any means. And there is a distinct fruity essence to this sauce that I can't quite put my finger on. Overall, not a great sauce, but definitely different.