The paper summarizes the development of limestone injection multistage burner (LIMB) technology in the U.S. Among many control processes tested in the U.S. for conformance with New Source Performance Standards (NSPS) was the injection of limestone into the furnace region of power boilers to capture sulfur oxides (SOx). These limestone injection removals never achieved NSPS levels, but its relative simplicity encouraged continued interest. The resulting EPA LIMB technology development program consists of several activities which, in large measure, have proceeded in parallel: (1) fundamental research, focusing on the kinetics of potential LIMB reactions and on properties of limestone and limestone products; (2) pilot scale research; (3) modeling; (4) engineering and cost analyses; and (5) process demonstration and commercial utilization.