St. Louis-style ribs are trimmed from what pork rib cut?

St. Louis-style ribs are trimmed from pork spare ribs.

A butcher creates the St. Louis cut by removing the sternum bone, cartilage, and rib tips from a rack of spare ribs. The result is a flatter, nearly rectangular slab that is easier to portion and present. Because the cut begins as spare ribs, the answer is not back ribs, country-style ribs, or beef short ribs.

Spare ribs come from the belly side of the pig’s rib cage, below the back ribs and above the breastbone. They are generally flatter and fattier than back ribs, qualities that help them remain flavorful during barbecue cooking. St. Louis trimming removes some irregular sections while leaving the main spare-rib rack.

Baby back ribs are a frequent source of confusion because they are also popular at barbecues, but they come from the upper rib cage near the loin and are shorter and more curved. Country-style ribs are usually cut near the shoulder or blade end and may contain shoulder meat rather than a conventional rib rack.