On Jan 14, 2019, the Foundations for Evidence-Based Policymaking Act of 2018 became law.
Known as the "Open Data Law", it requires federal agencies to publish their information online as "open data", using standardized, machine-readable data formats, with their metadata in the Data.gov catalog.
The topics cover a wide range of government functions.
The data catalog has links to web sites or repositories from the sponsoring agency.
In many cases, the data is not produced by the source but is curated by an organization as part of an international arrangement, e.g., meteorological or oceanic data.
Many Departments, Agencies, and Offices of the federal government have their own websites for providing open data in addition to using the central catalog.
These websites often have tools for visualizing the data as well as downloads.
Downloads options can include multiple formats: e.g., zip, csv, html, or Excel as well as special formats for mapping data.
Many sites allow for direct download via your browser while others may require FTP for large data sets.
Many locales have publicly-available data. A few examples: