At some national parks, the tours are more important than at others. Such is the case with Saugus Iron Works. The park is, mostly, a reconstruction of the iron works on the site from ~1646-1670; there is one house from shortly after the time of the iron works on the site, but we didn't visit it. (There's a separate tour that covers it.) The tour we did take - offered only once or twice a day - is rather amazing, showing how the blast furnace, forge, rolling and slitting mill, and a blacksmith shop in action; a ranger made nails, giving one to each of the children. The most impressive sight, though, was either the giant water wheel - or perhaps the smaller one that drove the 500 pound hammer.
All in all, it's very impressive; a much more active site than many of the historic locations. And - incredibly well removed from the city. So much so that a wedding party stopped by the site to take pictures, while we were there. It even managed to get Ben - who, being in surly teenager mode, didn't want to go - to admit that it was interesting.