Cream together the pumpkin and cream cheese until smooth.

Add the powdered sugar and cinnamon, and mix together until completely incorporated and no lumps are left.

Fold in the cool whip until the mixture is even throughout. The filling should be light and fluffy with consistent color.

Pour into your graham cracker crust, and place in the refrigerator to chill for at least an hour.

You can top with more cool whip, if desired. Slice and serve!