Citing Sources: Public Domain

Excerpt:
There are four common ways that works arrive in the public domain:
- the copyright has expired
- the copyright owner failed to follow copyright renewal rules
- the copyright owner deliberately places it in the public domain, known as “dedication,”
-copyright law does not protect this type of work.

"In the U.S., any work created by a federal government employee or officer is in the public domain, provided that the work was created in that person's official capacity."...
"Keep in mind that this rule applies only to works created by federal employees and not to works created by state or local government employees. However, state and local laws and court decisions are in the public domain."