The meridian 90° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, North America, the Gulf of Mexico, Central America, the Pacific Ocean, the Southern Ocean, and Antarctica to the South Pole. In Antarctica, the meridian defines the western limit of Chile's territorial claim. The land further west is not claimed by any nation. The 90th meridian west forms a great circle with the 90th meridian east, located midway between the Prime meridian and the 180th meridian; thus, the center of the Western Hemisphere is on this meridian. In the United States, the Mississippi River runs close to the 90th meridian, crossing the meridian several times. The cities of St. Louis, Memphis and New Orleans are all close to the meridian. One of the four 45 x 90 points is located in Rietbrock, Wisconsin, where the 45th parallel north intersects with the 90th meridian west, marking the halfway point between the 90° Latitude North, 180th Meridian East & West, 0° latitude, and 0° longitude.

From Pole to Pole

Starting at the North Pole and heading south to the South Pole, the 90th meridian west passes through: ! scope="col" width="120" | Co-ordinates ! scope="col" | Country, territory or sea ! scope="col" | Notes ! scope="row" style="background:#b0e0e6;" | Arctic Ocean ! scope="row" | 🇨🇦 ! scope="row" style="background:#b0e0e6;" | Nansen Sound ! scope="row" | 🇨🇦 ! scope="row" style="background:#b0e0e6;" | Norwegian Bay ! scope="row" | 🇨🇦 ! scope="row" style="background:#b0e0e6;" | Norwegian Bay ! scope="row" | 🇨🇦 ! scope="row" style="background:#b0e0e6;" | Barrow Strait ! scope="row" | 🇨🇦 ! scope="row" style="background:#b0e0e6;" | Prince Regent Inlet ! scope="row" | 🇨🇦 ! scope="row" style="background:#b0e0e6;" | Gulf of Boothia ! scope="row" | 🇨🇦 ! scope="row" style="background:#b0e0e6;" | Hudson Bay ! scope="row" | 🇨🇦 ! scope="row" | 🇺🇸 ! scope="row" style="background:#b0e0e6;" | Lake Superior ! scope="row" | 🇺🇸 ! scope="row" style="background:#b0e0e6;" | Gulf of Mexico ! scope="row" | 🇲🇽 ! scope="row" | 🇬🇹 ! scope="row" | 🇸🇻 ! scope="row" style="background:#b0e0e6;" | Pacific Ocean ! scope="row" style="background:#b0e0e6;" | Southern Ocean ! scope="row" | Antarctica