Great cities have great rivers, and the city of Philadelphia has two of the finest and most historic rivers in the United States: the Delaware and the Schuylkill.

Both have played critical roles in the American Revolution of the eighteenth century, the Industrial and Transportation Revolutions of the nineteenth century, and even the Environmental Revolution of the twentieth century.

At 330 miles long, the Delaware River is the longest free-flowing river east of the Mississippi and the third longest on the East Coast. The river and bay were named after Sir Thomas West (1577–1618), the 3rd Baron De La Warr and first governor of the colony of Virginia. The English erroneously thought that he had discovered the river, but there's no evidence that West ever saw or visited the Delaware.

The Delaware River was actually first explored by Henry Hudson (ca. 1570–ca. 1611), who called it "one of the finest, best, and pleasantest rivers in the world." He anchored in Delaware Bay on August 18, 1609, and claimed the country for the Dutch, as his trip to the New World was one of several he made to find a western route to Asia under the auspices of the Dutch East India Company.

At that time, the area around Delaware Bay was inhabited by the Lenape Native Americans. The Indian name for the bay was "Poutaxat". (They called the river itself "Lenape Wihittuck," which means "the rapid stream of the Lenape.")

The Dutch began calling the estuary Gogdijn's Bay (sometimes Godyn's Bay) after a director of the company, Samuel Godijn. As part of the New Netherland colony, the Dutch established several small settlements on the shores of the bay and explored its coast extensively. The Dutch were then calling the Delaware River the "South River."