The tri-tip steak comes from the tri-tip roast, which comes from the point where the sirloin meets the round and flank primals. Anatomically, the bottom sirloin is cut from low on the hindquarter, just in front of the hind legs.
The tri-tip is a small, triangular muscle, usually weighing between 1 1/2 and 2 1/2 pounds per side of beef. It was typically used for ground beef or sliced into steaks until it became a local specialty in Santa Maria, California in the late 1950s. Since then, the steak has become very popular for its full flavor, low cost and comparatively low fat content. It is sometimes known as the triangular steak and the Santa Maria steak.