Barack Obama expanded the monument by 442,781 square miles
An area of the Pacific Ocean has become the largest marine protected area on Earth.
The Papahanaumokuakea Marine National Monument is home to more than 7,000 marine species - including coral, fish, seals, turtles, whales, and several shipwrecks.
It also serves as the final resting place for more than 3,000 sailors and soldiers who served during World War II.
US President Barack Obama expanded the monument by 442,781 square miles - bringing the total protected area to 582,578 square miles and making it the world's largest marine protected area.
The Northwestern Hawaiian Islands were originally protected by former US President Teddy Roosevelt, who established the Hawaiian Islands Bird Reservation in 1909.
Franklin D. Roosevelt then broadened the protections to all wildlife and formed the Hawaiian Islands National Wildlife Refuge in 1940.
And in 2006, George W Bush created Papahanaumokuakea Marine National Monument to protect and preserve the marine waters and their wildlife.
The US government says this expansion comes after "significant engagement with the native Hawaiian community", the fishing industry, and residents of the islands.
"Today's historic action ensures the ongoing conservation of this iconic landmark. Throughout this process, we've collaborated with a number of stakeholders, including native Hawaiians, state and local officials, community leaders, and fishermen," said US Secretary of Commerce Penny Pritzker.
"The department is committed to protecting ecosystems like the Papahanaumokuakea Marine National Monument for future generations, and we are working with commercial fishermen to safeguard the continued economic vibrancy of this industry."