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Valley Forge National Park is located in Valley Forge, Pennsylvania, approximately eighteen miles west of Philadelphia and approximately two miles south of King of Prussia.

Physiographic Province Map of Pennsylvania

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PA Topographic & Geologic Survey
Copyright Commonwealth of Pennsylvania

Valley Forge National Park is located within the pale purple region on the Physiographic Map of Pennsylvania above known as the Piedmont Lowland Section. The Piedmont Lowland Section consists of broad valleys separated by broad hills. The Section is developed primarily on limestone and dolomite rock. Karst topography, characterized by sinkholes, caves, and underground drainage, is common. Local relief in the Section is generally less than 100 feet, but may be as much as 300 feet.   Elevations in the Section range from 170 feet to 630 feet. The park is bounded to the north by hills of red sedimentary rock which are part of the Gettysburg-Newark Lowland Section.   The south side of the park is bordered by a ridge of crystalline rock belonging to the Piedmont Upland Section.  This ridge provided Washington and his troops a defensible encampment from British invasion as enemy troops were stationed to the southeast in Philadelphia.

Topographic Map of Valley Forge, Pennsylvania

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Valley Forge Quadrangle; Pennsylvania 7.5 Minute Series
PA Topographic & Geologic Survey
Copyright Commonwealth of Pennsylvania

A topographic map is a map that depicts land elevation using lines of equal elevation called contour lines.  The patterns made by contour lines portray land forms, elevations, and slopes.  Closely spaced contour lines indicate a steep slope, widely spaced contour lines show show a gentle slope, and uniformly spaced contour lines indicate a uniform slope.  Contour lines at the top of a hill or mountain form a closed loop or circle.  

The brown lines on the topographic map of Valley Forge are contour lines and the interval between each line is 10 feet.  That is, there is a 10 foot change in elevation between any two contour lines on the map.  Can you pick out the hills and valleys of Valley Forge National Park?

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