The Northwestern Hawaiʻian Islands or the Leeward Islands are the small islands and atolls in the Hawaiian island chain located northwest (in some cases, far to the northwest) of the islands of Kauaʻi and Niʻihau. They are administered by the U.S. state of Hawaiʻi except Midway Atoll, which has temporary residential facilities and is administered by the U.S. Fish and Wildlife Service. In the state of Hawaii, they are part of the City & County of Honolulu. The United States Census Bureau defines this area as Census Tract 114.98 of Honolulu County. Its total land area is 8.0485 km² (3.1075 sq mi).

The Northwestern or Leeward Hawaiian Islands include:

• Nihoa at 23°03′38″N 161°55′19″W / 23.06056°N 161.92194°W / 23.06056; -161.92194
• Necker (Mokumanamana)
• French Frigate Shoals (Mokupāpapa)
• Gardner Pinnacles (Pūhāhonu)
• Maro Reef (Nalukakala)
• Laysan (Kauō)
• Lisianski (Papaʻāpoho)
• Pearl and Hermes Atoll (Holoikauaua)
• Midway (Pihemanu)
• Kure (Kānemiloha‘i) at 28°25′N 178°20′W / 28.417°N 178.333°W / 28.417; -178.333

The Northwestern Hawaiʻian Islands were formed over the same volcanic hotspot that formed the Emperor Seamounts to the north and the Main Hawaiʻian Islands to the south. As the Pacific Plate moved north and later northwest over the hot spot, volcanic eruptions built up islands. The isolated land masses gradually eroded and subsided, evolving from high islands in the south to atolls (or seamounts north of the Darwin Point).

Over 1,700 species of organisms are endemic to the NWHI, meaning they aren't found anywhere else in the world. For this reason, the region has been dubbed "America's Galapagos." Some of the endemic species include the Nihoa and Laysan Finch, the Laysan Duck (the rarest in the world), and the Nihoa fan palm. Other notable species are the Laysan Albatross, the highly endangered Hawaiian Monk Seal, and the Green Sea Turtle. Most endemic species are highly vulnerable to extinction as one major catastrophic event could wipe out all of the vegetation on each small island. Additionaly, seventy percent of all coral reefs in the United States are found here.

It is known that the Ancient Hawaiians ventured from the main islands as far as Mokumanamana (Necker), but they might have gone further to French Frigate Shoals. They were gone by the 1500s, though, when Europeans discovered the islands. Many agricultural terraces have been found on Nihoa, proving that they lived there long-term, but Mokumanamana, much barer of vegetation, was probably not able to support many people for long. It is thought that the early Hawaiians only came to Mokumanamana for religious purposes.

The majority of the Hawaiian names used as alternative to the English ones were created in modern times, in the same style as the Ancient Hawaiians would (had they discovered them). "Nihoa" and "Mokumanamana" are both names that were used by the Ancient Hawaiians; "Mokumanamana" being used equally often as "Necker." The rest of the Hawaiian names are hardly used. French Frigate Shoals' Hawaiian name "Mokupāpapa" is also a "real" name that was used by the Hawaiians, but it is not clear if they arrived here. It was originally heard in old chants and seems to fit the description, and this is the reason of the uncertainty as to how far they went, as it is not fully clear which island this was supposed to describe. It may have been a name for Johnston Atoll instead, but this is unlikely because it is much farther than French Frigate Shoals. The rest of the Hawaiian names were created in modern times.

On June 15, 2006, President George W. Bush issued a public proclamation creating Northwestern Hawaiian Islands National Monument under the Antiquities Act of 1906. The Monument encompasses the islands and surrounding waters, forming the largest marine wildlife reserve in the world. President Theodore Roosevelt had declared the Northwestern Hawaiian chain a bird sanctuary in 1909 and the islands had been protected since 2000 with a designation as an 'ecosystem reserve' by President Bill Clinton, but increasing it to national monument status provides unprecedented control. 139,000 square miles of ocean has been set aside for protection, about the size of the U.S. State of California.

Anyone who comes to the islands must follow stringent procedures designed to prevent any stray species from entering and disrupting the ecosystem. All clothes must be bought new, and kept wrapped until before arrival. In fact, all "soft" items (camera strap, blanket) must be bought new, and all "hard" items (camera, binoculars) must be cleaned thoroughly. Then, every item must be frozen for 48 hours. A new set of equipment must be prepared for each island one is going to, to prevent inter-island species introduction. However, French Frigate Shoals and Midway Atoll are exempted from these rules, as they are deemed too altered by humans already to worry about introducing new species.

• Hawaiian Islands National Wildlife Refuge
• Interactive Map from the PBS Ocean Adventures site
• Navigating Change
• National Monument NOAA Webpage

• Census Tract 114.98 and Block 1001 (Necker Island), Honolulu County, Hawaii United States Census Bureau