The following is from their website, http://www.api.org/
Beginning with its first standards in 1924, API now maintains some 500 standards covering all segments of the oil and gas industry. Today, the API standards program has gone global, through active involvement with the International Organization for Standardization (ISO) and other international bodies.
API is an American National Standards Institute (ANSI) accredited standards developing organization, operating with approved standards development procedures and undergoing regular audits of its processes. API produces standards, recommended practices, specifications, codes and technical publications, reports and studies that cover each segment of the industry. API standards promote the use of safe, interchangeable equipment and operations through the use of proven, sound engineering practices as well as help reduce regulatory compliance costs, and in conjunction with API’s Quality Programs, many of these standards form the basis of API certification programs.