The Philadelphia International Airport (code: PHL) is an important airport in Philadelphia, Pennsylvania. It is the biggest airport in the state and in the Delaware Valley. Starting around 1924 or 1925, the Pennsylvania National Guard began using what is now known as PHL (also called Hog Island) for a practice airfield. The site was later named the Philadelphia Municipal Airport, though it had no proper terminal building until around 1940. The name changed to Philadelphia International near the end of World War II. The airport has grown a lot over the decades.