BruceS:The National Park Service, the keeper of the the National Register is replacing their ailing NRIS database. The new database is
NPS Focus and is available to explore. Currently the only properties in the NPS Focus database are those sites listed as National Historic Landmarks or in the National Parks system (all NHL are listed but data has not been uploaded for all). The new site will be a great step forward as it includes the Nomination Forms (pdf and DjVu formats). I recommend the DjVu viewer.
Hopefully in addition to coverage for the NHL, they also add some NFL, MBA and MLB. Not really sure why your National Park Service has chosen to start highlighting professional sports but it seems in Canada our Parks Canada continues to focus on actual parks.
Maybe since these sports are played on fields and in parks, they have opened up their definitions... likely just to make some money though. Still, picking Hockey first seems like a very odd selection. Hardly thought of as an American pasttime and definitely NOT played on a field or in a park.
{yup... kidding of course]
BQ