On June 10, 1948, Charles Philamore Bailey, of Philadelphia, auspiciously performed the first anatomically conceived and digitally guided operation inside the heart: the first successful intracardiac operation. The patient, Claire Ward, was a 24-year-old woman afflicted with severe mitral stenosis. Dwight E. Harken and Russell C. Brock performed their own mitral operations very soon after Bailey, using new variations of methods that had been discarded about two decades earlier; they soon adopted the logical anatomic approach. This threesome, with the added contributions of Robert P. Glover--Bailey's partner at the time, in the role of respected and convincing teacher--opened the floodgates upon a decade of so-called closed heart surgery. These accomplishments, added to the earlier successes with the patent ductus, aortic coarctation, and "blue babies," justified and strengthened the demand for precise diagnosis in cardiology--at that time a languishing specialty--and brought to the fore the indisputable requirement to operate inside the heart with maximal control. This essay calls attention to the semicentennial of that seminal event and reviews the origins of surgery for mitral stenosis.