The Protected Areas Database of the United States (PADUS) is the official inventory of public parks and other protected open space. With more than 3 billion acres in 150,000 holdings, the spatial data in PAD-US represents public lands held in trust by thousands of national, State and regional/local governments, as well as non-profit conservation organizations.
It is possible to download data for the entire US or a state from the Data page. Data can be downloaded in Shapefile or Geodatabase format. A fact sheet can be found here. To view data in a viewer or download the data click below.