Nihoa & Mokumanamana

Nihoa and Mokumanamana, the two tiny islands closest to Kauaʻi, were home to Hawaiians from around AD 1000 to 1700. More than 135 archaeological sites have been identified, including temple platforms, house sites, agricultural terraces, burial caves and carved stone images. As many as 175 people may have once lived on Nihoa and paddled over to Mokumanamana for religious ceremonies.

That anyone could live at all on these rocks is remarkable. Nihoa is only 1 sq km in size, and Mokumanamana is one-sixth that size. Nihoa juts from the sea steeply, like a broken tooth; it's the tallest of the Northwestern Hawaiian Islands, with 900ft sea cliffs. Two endangered endemic land birds live on Nihoa. The Nihoa finch, which, like the Laysan finch, is a raider of other birds' eggs, has a population of a couple of thousand. The Nihoa millerbird, related to the Old World warbler family, numbers fewer than a thousand.

French Frigate Shoals

Surrounded by more than 230,000 acres of coral reef, these islets contain the monument's greatest variety of coral. They're also where most of Hawaii's green sea turtles and Hawaiian monk seals breed. The 67-acre reef forms a classic comma-shaped atoll on top of an eroded volcano, in the center of which 120ft-high La Pérouse Pinnacle rises like a ship. Small, sandy Tern Island is dominated by an airfield, which was built as a refueling stop during WWII. Today, Tern Island has a US Fish & Wildlife Service (FWS) field station housing scientific researchers and volunteers.

Laysan Island

Not quite 1.5 sq miles, Laysan is PMNM's second-biggest land mass. The grassy island has the most bird species in the monument, and to see the huge flocks of Laysan albatross, shearwaters and curlews – plus the endemic Laysan duck chasing brine flies around a supersalty inland lake – you'd never know how close this island came to becoming a barren wasteland.

In the late 19th century, humans began frequenting Laysan to mine guano (bird droppings) to use as fertilizer. Poachers also killed hundreds of thousands of albatross for their feathers (to adorn hats) and took eggs for albumen, a substance used in photo processing. Albatross lay just one egg a year, so poaching could destroy an entire year's hatch.

Traders also built structures and brought pack mules and, oddly enough, rabbits for food. The rabbits ran loose and multiplied, and within 20 years their nibbling mostly extirpated the island's 26 endemic plant species. Without plants, at least three endemic land birds – the Laysan rail, Laysan honeycreeper and Laysan millerbird – became extinct. Laysan finches and the last dozen Laysan ducks seemed doomed to follow.

In 1909, public outcry led President Theodore Roosevelt to create the Hawaiian Islands Bird Reservation, and the island has been under some kind of protection ever since. By 1923 every last rabbit was removed from Laysan, and ecological rehabilitation began. With weed-abatement assistance, endemic plantlife recovered, and so did the birds. The Laysan finch is again common, and the Laysan duck numbers about 600 (a smaller population has been established on Midway).

Nearly the same sequence of events unfolded on nearby Lisianski Island; together, these islands are a stunning success story.

Midway Atoll

Midway Atoll was an important naval air station during WWII. It's best known as the site of a pivotal battle in June 1942, when US forces surprised an attacking Japanese fleet and defeated it. This victory is credited with turning the tide in the war's Pacific theater. Midway later became a staging point for Cold War air patrols and an underwater listening post to spy on Soviet submarines.

By 1996 the military transferred jurisdiction to the FWS. Before leaving, it conducted an extensive clean-up program to remove debris, environmental contaminants, rats and non-native plants. Midway was then developed for tourism: barracks became hotel rooms, the mess hall a cafeteria, and a beachfront restaurant and bar were added. A gym, movie theater, bowling alley and library were part of the original military facility. On Sand and Eastern Islands, various military structures have been designated National Historical Landmarks.

The ecological highlight at Midway is the more than two million seabirds that nest here, including the world's largest colony of Laysan albatross, which are so thick between November and July that they virtually blanket the ground. Midway's coral reefs are unusually rich and are frequented by Hawaiian monk seals and green sea turtles.