
US Public Data.
Data USA API is a free Government API that requires no API key, is served over HTTPS and has unconfirmed CORS support.
The most comprehensive visualization of U.S. public data. Data USA provides an open, easy-to-use platform that turns data into knowledge.
Details from datausa.io.

Unified API suite · now live
Geocode an address, validate an email, track a flight or pull stock data with one account, one dashboard and one API key.
US Government Data
Contains live datasets including information about petitions, bills, MP votes, attendance and more
Colorado State Government Open Data
This API provides read access to DIP entities (e.g. activities, persons, printed material)
The Data USA API is provided by Data USA (datausa.io). The most comprehensive visualization of U.S. public data. Data USA provides an open, easy-to-use platform that turns data into knowledge.
Yes. The Data USA API is listed in the Government category of the public-apis directory, which only includes APIs that are free or have a free tier. Check its documentation for rate limits and paid plans.
No. The Data USA API requires no authentication, so you can start making requests without signing up.
CORS support for the Data USA API is unknown. Test a request from the browser, and fall back to a server-side call if it is blocked.
Yes. The Data USA API is served over HTTPS, so it's safe to use in production.