Between NW 17th and 24th Avenues, and between Burnside and Marshall Streets.
The Alphabet Historic District, an area zoned for historic preservation, extends roughly between NW 17th and 24th Avenues, and between Burnside and Marshall Streets.
Its naming scheme came about in 1865 when Captain John H. Couch platted his first subdivision. In 1891, the streets were assigned the names, each beginning with its respective letter, that they are known by today.
Alphabetical streets (some are just outside the district): Burnside, Couch, Davis, Everett, Flanders, Glisan, Hoyt, Irving, Johnson, Kearney, Lovejoy, Marshall, Northrup, Overton, Pettygrove, Quimby, Raleigh, Savier, Thurman, Upshur, Vaughn, and Wilson.
Links:
Wikipedia - Northwest District, Portland, Oregon - https://en.wikipedia.org/wiki/Northwest_District,_Portland,_Oregon
Travel Portland - Northwest Portland / Nob Hill - https://www.travelportland.com/collection/northwest-portland-nob-hill/