Maps of North America and copyrights

This is what the United States Digital Map Library says about copyrights.
"The Archives are intended for information that is in the Public Domain, i.e. that which is uncopyrightable, or the copyright has expired. The Digital Map Library will not knowingly place any file online that is under copyright, without permission of the copyright owner. In placing maps in the Archives, the following general guidelines have been used:

1.) ALL items with an ORIGINAL publishing or copyright date prior to 1923 are public domain. Anyone, including the United States Digital Map Library, may use them and distribute them freely.

2.) For items between 1923 and 1950, in order to still be copyrighted, the copyright holder must have renewed the copyright before the date it originally expired (a term of 28 years). However, because of the difficulty in determining the renewal of copyright for most documents of this period (as well as 1950 to present), it is required of the submitter to provide assurance of non-copyright for other than “public domain” materials."

The newer maps will be under copyright protection and should not be copied for commercial use.

Resources:

United States Digital Map Library. Accessed at: http://usgwarchives.net/maps/submissions.html