This historic location goes back to 1780, when the Earnest Fort House was built. The building was built in the European style by Swiss immigrant Henry Earnest (great information about him: http://www.genealogy.com/forum/surnames/topics/earnest/409/ ).
The cache is located near a hidden tupperware container, from another game of some kind. The cache you are looking for is not plastic. Actually, the new cache, as of Dec. 31, 2019, is made of plastic, a recycled pill bottle.
Be sure to enjoy all the historic and neat things in this part of the county.