As thousands of folks fly out of town after the Democratic National Convention, consider the ground upon which Philadelphia International Airport sits: Hog Island, once the world's largest shipyard.

Long before William Penn arrived aboard the Welcome in 1681, Swedish settlers controlled the island, at the confluence of the Delaware and Schuylkill. The Lenape called the island Quistconck, or "place for hogs."

Hog Island made a brief cameo during the American Revolution: An order in 1777 from the Council of Safety called for the island to be flooded, to halt British troops trying to infiltrate Philadelphia via the Delaware.

Banking, or diking, of the island allowed for agriculture to take root for much of the 1800s. By the beginning of the 20th century, enough dredge spoils had been deposited on the island that flooding was no longer a concern.

After America's entry into the First World War in April 1917, a sober appraisal was taken of the country's maritime force. To fight "over there," American men and materiel first had to be able to get over there. At the time, the vast majority of American exports were ferried by foreign ships. The country's merchant marine counted only 430 cargo and passenger ships.

To address this need, President Woodrow Wilson set out to transform Hog Island into the world's largest shipyard.

Beginning in the summer of 1917 and lasting through the winter, the island was shored up with more than a half-million cubic yards of gravel and soil from the Delaware's bed. Roads, railroads, electricity, and sewage facilities also had to be introduced. More than 35,000 "Hoggies" labored to build the shipyard.

"You'd work seven days a week for a month," said Frank Cautilli, a South Philadelphian who worked at the shipyard during the winter of 1917. "And then maybe you'd take a day off if you were really tired."

Hog Island's designation as a shipyard is perhaps misleading. "Shipbuilding" in its case consisted of riveting or welding together prefabricated parts. However, it was the first shipyard to use mass-production techniques on such a large scale.

Wilson's wife christened the Quistconck, the first ship assembled at Hog Island, on Aug. 5, 1918, barely three months before the war ended.

Due to construction delays, cost overruns, and other setbacks, not a single ship sutured together at the shipyard saw service during the conflict.

By the time of its closing in 1921, only 122 ships had been built at the $66 million facility.

Between 1930 and the mid-1950s, the grounds were subsumed by what was then known as Philadelphia Municipal Airport.

"The greatness of it, the bigness of it, was something to see," Cautilli said of the shipyard. "And it came from nothing but mud."

Geographically, Hog Island no longer exists: The Army Corps of Engineers filled in the creek that made it an island not long after the shipyard closed.

Gastronomically, however, its influence lives on. The submarine sandwich first served to workers at Hog Island - originally called a "Hoggie" - is perhaps better known by its other name: the hoagie.