Washingtons winter quarters in 1777 and 1778 were in Valley Forge, Pennsylvania. The site is located on the west bank of the Schuyikill river and is 22 miles from Philadelphia. Philadelphia was the capitol of the colonies at the time but was controlled by the British army.
The winter was extremely harsh one and the 11,000 troops encamped there suffered great hardships with hundreds dying from disease and exposure. Valley Forge is a National Park.