The US Well Number is the official successor to the API Well Number from the American Petroleum Institute (API). In 2010, the API transferred custody of their standard to the PPDM Association. The new standard provides continuity with the API Number while addressing some challenges that have evolved in the past four decades: well designs and data flows have become more complex, safety and environmental risks have increased where unidentified wellbores are present, and data exchange is difficult if identifiers are assigned inconsistently.