Published by the American Geophysical Union as part of the Field Trip Guidebooks Series, Volume 209. Rock Creek Park is a special place for studying geology. Founded as the city park in 1890, Rock Creek Park serves as an oasis in the urban environment. Rock Creek Valley is a steep craggy Piedmont eroded zone where one can observe the bedrock, follow the evolution of the Fall Zone,and measure the topographically isolated Coastal Plain gravels. Figure 1 is the map of the stops to observe the general geology.