PDX (Portland nickname)

The city of Portland is sometimes called “PDX” after the airport code (cited in print since at least 1948-49) for Portland International Airport. In 1987, Portland State University chose the Internet domain name “pdx.com” because Pennsylvania State University had taken “psu.com.”
 
“PDX” has been printed on many clothing items.
     
 
Wikipedia: Nicknames of Portland, Oregon
PDX
The city of Portland is nicknamed PDX after the International Air Transport Association airport code for the Portland International Airport which is within the city limits. For example, the domain name for Portland State University of pdx.edu was chosen in 1987, since psu.edu had already been given to Pennsylvania State University in the previous year.
 
Wikipedia: Portland International Airport
Portland International Airport (IATA: PDX, ICAO: KPDX, FAA LID: PDX) is a joint civil-military airport and the largest airport in the U.S. state of Oregon, accounting for 90% of passenger travel and more than 95% of air cargo of the state.[2] It is located within Portland’s city limits just south of the Columbia River in Multnomah County, six miles by air and twelve miles by highway northeast of downtown Portland. Portland International Airport is often referred to by its IATA airport code, PDX.
     
Google Books
Air Transportation
Volumes 12-13
1948
Pg. 74:
PDX— Portland, Ore.
 
Google Books
Airline Traffic Procedures
By Gene Kropf
New York, NY: McGraw-Hill Book Co.
1949
Pg. 367:
PDX…Portland, Ore
 
13 January 1964, The Oregonian (Portland, OR), “No Kickback,” pg. 20, col. 1:
Every major airport has its three-letter code, closely derived from its formal name, to simplify communications, baggage handling, ticketing and the like. Thus, Seattle is SEA, Portland is PDX, San Francisco is SFO, Los Angeles is LAX and Idlewild has been IDL.
   
Google Books@ Large:
The strange case of the world’s biggest Internet invasion
By David H. Freedman and Charles C. Mann
New York, NY: Simon & Schuster
1997
Pg. 101:
Similarly, pdx.edu is the domain name for Portland State University, an educational institution; cs.pdx.edu was the network at the Portland State computer-science department. (The name “pdx,” incidentally, came from the three-letter symbol for the Portland airportm because psu.edu, the obvious domain name, belongs to another PSU, Pennsylvania State University.)
 
Google Books
USA
By Jeff Campbell, et al.
London: Lonely Planet
2008
Pg. 1028:
PORTLAND
Call it what you want—PDX, P-town, Stumptown, City of Roses, Bridge City or Beervana—Portland positively rocks.