The St. Louis pork steak sandwich is barbecue that starts with a butcher's cut, not a whole muscle held for hours. The pork steak is a slice of the shoulder cut across the bone and the marbling, roughly the same anatomy that becomes pulled pork, but treated as a steak rather than a roast. That single decision changes the whole sandwich. There is a hard grilled edge on every slice, the meat keeps a sliceable structure instead of collapsing into shreds, and the bone-adjacent fat bastes the cut from the inside while it cooks. This is what separates it from the pulled-pork sandwich it is constantly mistaken for: same animal, same shoulder, completely different texture in the hand.
The method is two-stage and the order matters. The steaks go over direct heat first to set a charred crust and render the heavy fat seams, then they are moved into a covered pan and braised low in a thinned tomato-and-vinegar sauce until the connective tissue gives. The sauce is doing structural work as much as it is seasoning: the braise keeps a lean shoulder slice from drying out after the grill has already driven moisture off the surface, and it pulls the rendered fat and char into a clinging glaze. On soft white bread the assembly is plain on purpose. The bread is a holder and a sauce sponge, the meat overhangs it, and a slice or two folds into the sandwich with enough sauce-soaked crumb to bind the bite without competing with the smoke and the vinegar.
The sandwich stays close to its own city and its own sauce, and the sweet, slightly tangy local style is part of why it reads the way it does. Variations exist along the obvious lines: a sweeter glaze, a sharper vinegar cut, a heavier char from a longer first stage, the steak left whole on the plate rather than folded into bread. The wider American barbecue argument, the Carolina vinegar schools, the Texas brisket position, the Kansas City sauce case, runs alongside this one rather than through it, and those deserve their own articles rather than being crowded in here.