The mission of the National Geodetic Survey (NGS) is to “define, maintain and provide access to the National Spatial Reference System to meet our nation's economic, social, and environmental needs.” One component of that mission is to provide accurate geodetic control, including a vertical datum, for all territories of the United States. The islands of the territory of Puerto Rico have had a mixed, patchwork series of geodetic control over the last century, when they have had any geodetic control at all. This has included the lack of a comprehensive vertical datum for the entire territory. In accordance with its mission, NGS underwent an effort beginning in 1993, which has culminated in the Puerto Rico Vertical Datum of 2002. This paper defines that datum and describes the work leading up to its definition.