life:

A half-century ago, on a spring night in New York City, 35-year-old Marilyn Monroe — literally sewn into a sparkling, jaw-droppingly tight dress — stood in a spotlight on a dark stage. She took a breath, began to sing — and 15,000 men and women who filled the old Madison Square Garden that night knew, simply knew, that they were seeing and hearing something that they would never, ever forget.

The song, of course, was “Happy Birthday,” and Marilyn’s breathy, intimate rendition — sung, as if the two of them were utterly alone, to President John F. Kennedy — has been celebrated, analyzed and lovingly parodied countless times in the five decades since that indelible performance.

LIFE’s Bill Ray was there — and now, we present a set of unpublished from that unforgettable night.

(via timelightbox)