The airport was built by the Port of Seattle in 1944 after the U.S. military took control of Boeing Field in World War II.
The Port received $1 million from the Civil Aeronautics Administration to build the airport and $100,000 from the City of Tacoma.
The first scheduled airline flights were Northwest and Trans-Canada in 1947; Western and United moved from Boeing Field in the next couple of years, and Pan Am moved in 1952–53, but West Coast and successors Air West and Hughes Airwest stayed at Boeing Field until 1971.
The original terminal was designed by architect Herman A. Moldenhour.
The official opening ceremony took place on July 9, 1947 in front of a crowd of 30,000.

In June 1951 four runways were at 45-degree angles, between 5,000 and 6,100 feet (1,500 and 1,900 m) long; the northeast-southwest and northwest-southeast runways intersected just west of the north-south runway that eventually became today's runway 34R. Runway 34 was lengthened to 7500 ft in 1951, to 8500 ft by 1958, and to 11900 ft by 1962.
The extension required the construction of an automobile tunnel for South 188th Street, which opened in July 1961.
Runway 34L replaced runway 2 around 1970.

The April 1957 OAG shows 216 departures a week on United, 80 Northwest, 35 Western, 21 Trans-Canada, 20 Pan Am, 20 Pacific Northern and 10 Alaska.
The first jet flights were Pan Am Boeing 707s to Honolulu via Portland (OR) in late 1959 (Pan Am's timetable for September 27 shows a weekly jet).
In 1966 Scandinavian Airlines began the airport's first non-stop flight to mainland Europe (Pan Am nonstops to London began around 1961).
The first concourse opened in July 1959.

The two-story North Concourse (later dubbed Concourse D) added four gate positions and a new wing 600 feet (180 m) long and 30 feet (9.1 m) wide.
The one-story South Concourse (now Concourse A) opened in 1961, adding another 688 feet (210 m) to the length of the airport.
The 800-foot (240 m) long Concourse B opened in December 1964.
It added eight gate positions, bringing the total to 19, a 12,000 square feet (1,100 m²) area housing international arrivals and the offices of U.S. Customs, Immigration, Public Health and the Department of Agriculture.
Concourse C opened in July 1966.
Just four years later, it was extended to include another 10 gates, bringing the total to 35.
The Port embarked on a major expansion plan, designed by The Richardson Associates and lasting from 1967 to 1973, adding a second runway, a parking garage, two satellite terminals and other improvements.
In 1973, $28-million new terminal was built over and around the 1949 structure; the new terminal quadrupled the area for public use.
On July 1, 1973, the Airport opened two new satellite terminals, along with an underground train system to connect them to the Main Terminal.
In the mid-1980s, the Main Terminal was renovated and another 150 feet (46 m) was added to the north end.
Concourse D was expanded in 1987 with a rotunda that added four new gates.
In 1993, Concourses B, C, and D were renovated.
The project, designed by NBBJ, included the addition of 150,000 square feet (14,000 m²) and the renovation of 170,000 square feet (16,000 m²) of space in Concourses B, C, and D. On June 15, 2004, the 2,102-foot (641 m) new Concourse A was unveiled with 14 new gates, a dozen new restaurants, new artwork and the airport's first moving sidewalks.

Residents of the surrounding area filed lawsuits against the Port in the early 1970s, complaining of noise, vibration, smoke, and other problems.
The Port and the government of King County adopted the Sea–Tac Communities Plan in 1976 to address problems and guide future development.
The Port spent more than $100 million over the next decade to buy homes and school buildings in the vicinity, and soundproof others nearby.
In the mid-1980s, the airport participated in the airport noise-compatibility program initiated by Congress in 1979.
Airport-noise contours were developed, real estate was purchased and some homes were retrofitted to achieve noise mitigation.

In 1978 the U.S. ended airline regula
The airport was built by the Port of Seattle in 1944 after the U.S. military took control of Boeing Field in World War II. The Port received $1 million from the Civil Aeronautics Administration to build the airport and $100,000 from the City of Tacoma. The first scheduled airline flights were Northwest and Trans-Canada in 1947; Western and United moved from Boeing Field in the next couple of years, and Pan Am moved in 1952–53, but West Coast and successors Air West and Hughes Airwest stayed at Boeing Field until 1971. The original terminal was designed by architect Herman A. Moldenhour. The official opening ceremony took place on July 9, 1947 in front of a crowd of 30,000.
In June 1951 four runways were at 45-degree angles, between 5,000 and 6,100 feet (1,500 and 1,900 m) long; the northeast-southwest and northwest-southeast runways intersected just west of the north-south runway that eventually became today's runway 34R. Runway 34 was lengthened to 7500 ft in 1951, to 8500 ft by 1958, and to 11900 ft by 1962. The extension required the construction of an automobile tunnel for South 188th Street, which opened in July 1961. Runway 34L replaced runway 2 around 1970.
The April 1957 OAG shows 216 departures a week on United, 80 Northwest, 35 Western, 21 Trans-Canada, 20 Pan Am, 20 Pacific Northern and 10 Alaska. The first jet flights were Pan Am Boeing 707s to Honolulu via Portland (OR) in late 1959 (Pan Am's timetable for September 27 shows a weekly jet). In 1966 Scandinavian Airlines began the airport's first non-stop flight to mainland Europe (Pan Am nonstops to London began around 1961). The first concourse opened in July 1959.
The two-story North Concourse (later dubbed Concourse D) added four gate positions and a new wing 600 feet (180 m) long and 30 feet (9.1 m) wide. The one-story South Concourse (now Concourse A) opened in 1961, adding another 688 feet (210 m) to the length of the airport. The 800-foot (240 m) long Concourse B opened in December 1964. It added eight gate positions, bringing the total to 19, a 12,000 square feet (1,100 m²) area housing international arrivals and the offices of U.S. Customs, Immigration, Public Health and the Department of Agriculture. Concourse C opened in July 1966. Just four years later, it was extended to include another 10 gates, bringing the total to 35. The Port embarked on a major expansion plan, designed by The Richardson Associates and lasting from 1967 to 1973, adding a second runway, a parking garage, two satellite terminals and other improvements. In 1973, $28-million new terminal was built over and around the 1949 structure; the new terminal quadrupled the area for public use. On July 1, 1973, the Airport opened two new satellite terminals, along with an underground train system to connect them to the Main Terminal. In the mid-1980s, the Main Terminal was renovated and another 150 feet (46 m) was added to the north end. Concourse D was expanded in 1987 with a rotunda that added four new gates. In 1993, Concourses B, C, and D were renovated. The project, designed by NBBJ, included the addition of 150,000 square feet (14,000 m²) and the renovation of 170,000 square feet (16,000 m²) of space in Concourses B, C, and D. On June 15, 2004, the 2,102-foot (641 m) new Concourse A was unveiled with 14 new gates, a dozen new restaurants, new artwork and the airport's first moving sidewalks.
Residents of the surrounding area filed lawsuits against the Port in the early 1970s, complaining of noise, vibration, smoke, and other problems. The Port and the government of King County adopted the Sea–Tac Communities Plan in 1976 to address problems and guide future development. The Port spent more than $100 million over the next decade to buy homes and school buildings in the vicinity, and soundproof others nearby. In the mid-1980s, the airport participated in the airport noise-compatibility program initiated by Congress in 1979. Airport-noise contours were developed, real estate was purchased and some homes were retrofitted to achieve noise mitigation.
In 1978 the U.S. ended airline regula
Seattle–Tacoma International Airport