Source

Library of Congress

Early films, newsreels and government footage, much of it public domain. Link-only: its search API is rate-limited and challenges cloud IPs.

Licence: Set per clip
Pricing: Free
Direct download: No, results link to the source site
Footage: Archive & vintage, People, City & urban, Transport
How it is searched: Not searched directly: the site does not allow automated search, so results link to the same search on the site

What Library of Congress is

The Library of Congress holds early films, newsreels and US government footage, much of it in the public domain.

Early American film, government and historical footage.

Set per item; many films are public domain or have no known restrictions, but check each item's rights statement.

Link only: its search API is tightly rate-limited and challenges requests from cloud servers, so every search links to the same query on loc.gov.