Jeremy Swan and William Ganz developed their eponymous pulmonary artery (PA) catheter in the 1970s and, in the process, revolutionized measurement of cardiac output, pressures within the left side of the heart, and resistance in systemic and pulmonary circulations. Their invention enabled diagnostic measurements at the bedside and contributed to the birth of critical care medicine; technologic advances preceding the PA catheter generally could not be used at the bedside and required patients to be stable enough to be taken to the catheterization laboratory. Swan and Ganz worked in the same department but had quite dissimilar backgrounds and personalities. This article describes their lives and careers, the state of intensive care before and after their catheter was introduced, and the natural life cycle the PA catheter faced as new, less invasive technology arrived to replace it.