Henry Mercer collected pre-industrial hand tools and other implements of the past. He believed that the story of human progress and accomplishments was told by the tools and objects that people used and saw these time-honored crafts slowly disappearing from memory. Basically an old tool otaku. It's very cluttered, but pretty well organized. It's very different than any other museum I've seen.
It's built out of poured in place concrete. He was mocked for this. To spite them, he built a bonfire on the roof to show it was fireproof. Interesting guy.
Nearby is the Moravian Pottery and Tile Works, also built by Mercer. They still make and sell really nice tiles.