When was Valley Forge built and used by soldiers?

Valley Forge was never built as a monument. Is a historical monument from the Revolutionary War. There are some Huts that were built around that time. Most of the housing and buildings in the area or private homes that were used or, as you will, commandeered during the war.

Congress was supposed to have this encampment ready for Washington and the roughly 10k soldiers under his command before they arrived here. Tragically enough when they arrived in Valley Forge they found that not a single hut was built. There was also no food sources as promised by Congress. Starving and many without proper winter clothing and many others without shoes, our great man and women built their quarters and had to travel as far as Lancaster to find food for the Army. By the time they departed camp in June of 1778, the camp had grown to around 20 thousand men and women.

The Valley Forge encampment was used by the Continental Army during the winter of 1777-78.

1777, and 1778

To combine the previous answers: the original encampment was built and used by the Continental Army over the winter of 1777-1778.

During the winter of 1777