Revisiting this thread since I'm currently working on larger versions of my maps that cover the whole Northeast US region. I need openspace data for all those states and it's a real run-around trying to find it on individual state websites. So, this looks like a very good option for getting all the data in one place. You can download the current Protected Area Database (PAD) here
Download the Protected Areas Database (PAD-US) Data:Data are available for download in an ArcGIS Geodatabase format Nationally or by 56 State/Territory boundaries.
www.usgs.gov
I downloaded the full US file, but it's absolutely huge and almost impossible to work with. After 30 minutes, my GIS program still hadn't loaded the whole thing, so I gave up. But you can download individual state versions here and they work well, so that's what I'm using.
In addition to the national download available in PAD-US 4.0, data is available by 56 State/Territory boundaries in GBD format. The U.S. Census Bureau is the national steward for legally defined geographic area boundaries for State and Equivalent areas. For more information about Census...
www.sciencebase.gov
There's a lot of data here and I need to study more carefully, because not everything on these maps is actually *public* openspace. I think it also includes areas that *should* be protected in some way, so I will need to filter this kind of thing out before creating my maps. This is from the metadata:
"The PAD-US geodatabase was originally developed to organize and assess the management status of elements of biodiversity protection by identifying species and plant communities not adequately represented in existing conservation lands."
Here's an example of the attrbutes available from a portion of Wharton State Forest, for example
But this is also part of the database, and not someplace you can wander around.
Anyway, this may not be useful to anyone else, but thought I'd post here for future reference. The data is supplied as ArcGIS GDB files, so you would need software capable of opening those kinds of files to utilize these downloads.