Thirty-two years ago yesterday, after years of congressional debate, President Jimmy Carter signed into law the Alaska National Interest Lands Conservation Act (ANILCA). The statute protected more than 100 million acres of federal lands in Alaska, doubling the size of the country’s national park and refuge system and tripling the amount of land designated as wilderness. With the passage of ANILCA, Alaska’s national park system expanded by more than 43 million acres. Ten new national parks were created, and three existing units were enlarged. It’s no wonder it’s often called the most significant land conservation measure in the history of our nation.

Pulling off this monumental piece of legislation, however, was a painstaking process. Between 1977 — when it was first introduced in the U.S. House of Representatives — and 1980, more than a dozen drafts of ANILCA were considered. And today, more than 30 years later, battles rage on in Congress and courts over the interpretation of some of its key provisions.

Understanding the controversy surrounding this statute requires a careful look at how it came to be. In 1959, when Alaska became a state, the vast majority of its land was federally owned. The Statehood Act granted the state government the right to select more than 100 million acres of land to manage as a revenue base, and it began to stake out land. Many of its selections, however, inevitably overlapped with Alaskan Natives’ territories. Pressured from the native community, Steward Udall, the Secretary of the Interior, declared a land freeze. And with this, the state’s development came to a screeching halt. The oil industry, the Nixon administration and the state of Alaska, consequently, began to advocate on behalf of the natives. And in 1971, the Alaska Native Claims Settlement Act (ANCSA) authorized Native corporations to select 44 million acres of federal lands in Alaska. (There is currently a debate in Congress to re-open this act. Learn more about what’s at stake and how you can weigh in.)

Throughout these negotiations, the environmental community expressed concern that Alaska’s lands were being appropriated with too great an emphasis on development. These concerns are reflected in Section 17 of ANCSA, which requires the withdrawal of up to 80 million acres of significant federal lands from development to be considered for designation as national parks, wildlife refuges, wild and scenic rivers or national forests. This provision, however, came with a deadline. If Congress did not act to protect these lands by 1978, they would once again become available for development.

Finally, six long years later — one year before the deadline — Congress introduced the first version of ANILCA. Contentious negotiations dragged on as the ANSCA deadline approached, so the Carter administration made a bold move in 1978 and withdrew more than 100 million acres of federal lands from development. This decision ensured that the deadline would be met, as an Alaskan lands bill would now be necessary for the Alaskan congressional delegation to determine the use of these public lands, and Congress passed the final version of ANILCA on December 2, 1980. So, happy birthday to Denali National Park, St. Elias National Park and Preserve, Gates of the Arctic National Park and Preserve, Lake Clark National Park and Preserve, Kobuk Valley National Park, Katmai National Park and Preserve, Glacier Bay National Park and Preserve … well, you get the point.