Greenwood Furnace is a Pennsylvania State park (not a national park). You can visit here for free. Check the national park website for info on national park passes (nps.gov)
Go to nps.gov and from the menu select Passes. There is a list of places to buy the pass, or you can do the whole thing online (extra cost for that, for some reason).
You can go online and order from National Park Senior pass you will get all the information on there
Gary, Greenwood Furnace is a State Park. Do a search for National Parks and call. Happy travels!
If you can get a lifetime pass you'd need to contact NPS. Greenwood Furnace is a state park, not a national park. It's a nice park to visit and daytime use of the park is free. You have to pay if you want to reserve a pavilion or camp but you can visit for nothing.
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