Map of the plan of the city of Philadelphia. The city is largely composed of north south and east west streets intersected at right angles. The Delaware River is to the south. Public Domain

Map of the plan of city of Washington. Streets are laid out in orderly, straight lines, running east west and north south. There are some diagonal streets. The Potomac and Eastern Branch of the Potomac form the southwest and southeast borders, respectively. At the intersection of diagonals are open spaces and the National Mall is clearly visible, running from the Potomac east to the center of the city.
Public Domain

This map, from 1792, is a plan for the city of Washington D. C. How is it related to Philadelphia?

Both cities were planned by Charles L'Enfant.
Both cities were built at the intersection of major rivers.
Both cities were constructed in the late 1700s.
Both cities were planned using the grid system.