According to the United States Copyright Office, a “work of authorship is in the ‘public domain’ if it is no longer under copyright protection or if it failed to meet the requirements for copyright protection. Works in the public domain may be used freely without the permission of the former copyright owner."
Stanford University Libraries explains there are 4 common ways that works enter into the public domain:
Video from the United States Copyright Office: "The public domain covers works not protected by copyright. Learn which works are in the public domain and how works become a part of it."
The staff of the Digital Initiatives department at the North Dakota State Library are not lawyers, nor are they copyright experts. Digital Initiatives will provide help to the best of their ability, but any information provided does not constitute legal advice.
Many of these resources and programs are funded under the provisions of the Library Services and Technology Act from the Institute of Museum and Library Services.