as noted, Category:Valley Forge is marked as mis-named, most likely because it is too vague, and the Category:Valley Forge, Pennsylvania may be the one that was intended to replace it as it adds the state to further identify it. While most of us think of Valley Forge as the Rev War camp for the Continental Army, it took the name of the nearby, and still in existence, town of Valley Forge, so using that category could lead to confusion if someone starts adding present day info about the town, park, etc to it.
We have Category: US Forts, Camps and Bases which is used to identify mostly existing sites, but some are there that are no longer in use as well, but usually in use for an entire war/longer period of time
Since Valley Forge was essentially winter quarters and used for just that winter 1777 period, it does make more sense to keep it under the war specific context and not in the overall US Forts, Camps and Bases. To me it would fall under
Category: American Revolution
Category: Continental Army
Category: Continental Army Military Camps
Category: Valley Forge, Winter Encampment
if this looks good to everyone, I can send it over to categorization team to make sure the format is acceptable to them.