Portland's first airport was the Swan Island Municipal Airport, northwest of downtown Portland on the Willamette River. The Port of Portland purchased 256 acres (104 ha) and construction began in 1926. Charles Lindbergh flew in and dedicated the new airfield in 1927.

By 1935 it was becoming apparent to the Port of Portland that the airport was becoming obsolete. The small airfield couldn't easily be expanded, nor could it accommodate the larger aircraft and passenger loads expected to become common to Portland. Plans immediately were conceived to relocate the outdated airfield to a larger site. The Swan Island area is now used by the Port of Portland as an industrial park.

Portland International Airport was officially opened on October 13, 1940, initially as Portland-Columbia Airport.

Construction and early operations

The Portland City Council purchased the present PDX site in 1936. It was 700 acres (280 ha) bordered by the Columbia River in the north and the Columbia Slough in the south. The city council issued US$300,000 and asked the Port of Portland to sponsor a US$1.3 million Works Progress Administration (WPA) grant to develop the site into a "super airport". The project provided badly needed Great Depression-era jobs. Construction of the airport steadily employed over 1,000 men, and was described by historian Neil Barker as "Portland's most significant public works improvement during the New Deal era". The WPA and Port of Portland faced difficulties in preparing the site for construction because the low-lying area was frequently covered by flood waters from the Columbia River. Workers covered the area with over 4 million cubic yards (3,100,000 m3) of sand to help drain it of water, and constructed a series of dikes to control flooding. Two runways capable of serving the modern aircraft of the time were operational by 1941. The airport was designated "Portland–Columbia Airport" to distinguish it from then-operating Swan Island Airport. During World War II, the airfield was used by the United States Army Air Forces.

The "super airport" had a terminal on the north side, off Marine Drive, and five runways (NE-SW, NW-SE, and an E-W runway forming an asterisk). This configuration was adequate until a new terminal and a longer, 8,800-foot (2,700 m) east–west runway were constructed in 1952.

In 1948, the entire airport grounds were flooded during the Vanport Flood, forcing scheduled airline services to reroute to nearby Troutdale Airport. The grounds were under water for several months.

New terminal (1950s)

Portland's first jets were Pan Am 707-321s about October 1959. A new terminal opened in 1959, which for the most part serves as the present facility. The new terminal is located to the east of the original runways, and north of the then-new 8,800 ft (2,700 m) runway. Construction of a second east–west runway to the north made this a midfield terminal. At this point, all but the NE-SW (3/21) runway in the original "X" were abandoned and turned into taxiways. 3/21 was extended for use as a cross-wind runway. "International" was added to the airport's official designation after the 1950s-era improvements.

The first international nonstop was Western's 720B to Vancouver, British Columbia, in 1967. Plans made in 1968 to add a third runway by means of filling in parts of the Columbia River were met with vocal public opposition and scrapped. The airport switched from screening passengers at individual gates to screening all visitors at concourse entrances in 1973 as new FAA regulations went into effect. By 1974, the airport was served by Braniff, Cascade, Continental, Eastern, Hughes Airwest, Northwest Orient, Pan Am, United and Western, and the Seattle route was served by seven airlines with aircraft as large as Boeing 747s. In 1974, the south runway was extended to 11,000 feet (3,400 m) to service the newest jumbo jets. The terminal building was renovated and expanded in 1977.

United was the dominant carrier at PDX during the regulated era and through the 1980s. Air Oregon started short-haul service from Portland following deregulation in 1978, and by 1979 had routes to seven other cities in Oregon. In April 1983, United Airlines began a flight from Chicago to Tokyo's Narita Airport that stopped in Seattle–Tacoma six days a week and in Portland once a week. The company operated the service with Boeing 747s. Meanwhile, Delta Air Lines wanted to add Tokyo to its network, but it lacked aircraft that could fly there nonstop from its Atlanta base. Consequently, the company established a "Pacific gateway" in Portland, a small hub for routes to Asia. Delta began service from Portland to Tokyo in March 1987.

By the 1980s, the terminal building began an extensive renovation in order to update PDX to meet future needs. The ticketing and baggage claim areas were renovated and expanded, and a new Concourse D for Alaska Airlines was added in 1986. Concourse E was first to be reconstructed in 1992, and featured PDX's first moving sidewalks. The Oregon Marketplace, a small shopping mall, was added in the former waiting areas behind the ticket counters.