Data.gov publishes 552,271 open datasets for United States. Browse them live in Vizzie and turn any one into a map or chart.
Data.gov is the open-data portal for United States. It runs on CKAN, an open catalogue standard used by many national governments. You can browse it directly at catalog.data.gov. Reuse terms are set out in the portal's terms of service (Federal works are US public domain, but harvested state/local records carry their own licences.).
Licences here are declared per dataset via Per-dataset; US federal works are public domain. A machine-readable summary of the licence mix isn't available yet, but Vizzie surfaces each dataset's declared licence (or notes when none is given) as you browse — remember that an undeclared licence is not the same as public-domain or free-to-use, so check before you reuse.
Metadata-only catalogue. Federal works public domain; harvested state/local records carry their own licences — read per-dataset licence, don't assume US-PD for non-federal publishers.
Data.gov doesn't expose a machine-readable breakdown of who publishes what, so there's no reliable publisher ranking to show here. Vizzie still surfaces each dataset's own publisher as you browse.
No download, no GIS specialist. Opens in Vizzie.