National Airport in Arlington was opened in the summer of 1941, several months before Pearl Harbor. Below is a fascinating old image showing the aerial view of what would eventually become National Airport.

Oblique aerial view looking roughly north-northeast from above Dangerfield Island of dredge and fill activities in the Gravelly Point area of the Potomac River for construction of Washington National Airport (DCA); October 28, 1939. Annotations in white indicate the future boundaries of the airport, the runways, and the relocated path of the George Washington Parkway (left) and identify the dredges Gulf Stream, Talcott, Lake Ellendale, and Pennsylvania. Memorial Bridge is visible in the background at top left, and the Washington Monument and the Mall area of Washington, DC, at top center.
Oblique aerial view looking roughly north-northeast from above Dangerfield Island of dredge and fill activities in the Gravelly Point area of the Potomac River for construction of Washington National Airport (DCA); October 28, 1939. Source: Smithsonian