also north-west, Old English norþwest (adv.) "to a point or in a direction between north and west;"  from north + west. As a noun, "region or locality lying in the northwest of a country," and adjective from late 14c.

In U.S. geography it was at first, the territory that later became Ohio, Indiana, Illinois, Wisconsin, Michigan and northeastern Minnesota (1787); after about 1853 the term was applied to the unorganized territory north of Nebraska, west of Minnesota, and east of the Rockies. Pacific Northwest, describing Oregon and Washington, is by 1874. Related: Northwestern; northwesterly; northwestward (late 14c.).

Northwest Passage as the name of an at-first hypothetical sea route from the Atlantic to the Pacific by the northern coasts of North America, first attested c. 1600. The Northwest Ordinance (1787) was an act of Congress to organize the territory beyond the Appalachian Mountains between the Great Lakes and the Ohio River.

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Definitions of northwest
northwest (n.)
the direction corresponding to the northwestward compass point;
northwest (n.)
the compass point midway between north and west; at 315 degrees;
Synonyms: nor'-west / northwestward / nw
northwest (n.)
a location in the northwestern part of a country, region, or city;
northwest (adj.)
situated in or oriented toward the northwest;
Synonyms: northwestern / northwesterly
northwest (adj.)
coming from the northwest;
Synonyms: northwesterly
northwest (adv.)
to, toward, or in the northwest;
Synonyms: north-west / nor'-west
Northwest (n.)
the northwestern region of the United States;
Synonyms: northwestern United States