The US Congress was urged to create the exemption by proponents of a conservation plan on San Bruno Mountain, California that was drafted in the early 1980s and is the first HCP in the nation. In the conference report on the 1982 amendments, Congress specified that it intended the San Bruno plan to act "as a model" for future conservation plans developed under the incidental take exemption provision and that "the adequacy of similar conservation plans should be measured against the San Bruno plan". Congress further noted that the San Bruno plan was based on "an independent exhaustive biological study" and protected at least 87% of the habitat of the listed butterflies that led to the development of the HCP.