Here is a reminder to help you answer the above question:

Works published in the U.S. with copyright owner's consent prior to 1923 have already reverted to public domain status. Works not published in the U.S. with the copyright owner's consent prior to 1978 may be protected for the life of the artist plus seventy years. Hence, most historic works of art are not subject to copyright in the United States.

The folowing link provides an in depth summary of Copyright
Duration and U.S. Law:

• Summary of Copyright Duration and U.S. law
You may wish to use the following resource links and references to help answer the above question:

• What Does Copyright Protect?
(USCO: Frequently Asked Questions About Copyright)

• What Works Are Protected by Copyright?
(USCO: Circular 1, Copyright Basics: see "What Works Are Protected," p. 3)

• Does Copyright Protect Architecture?
(USCO: Circular 41: Copyright Claims in Architectural Works)

• What Is Publication?
(USCO: Circular 1, Copyright Basics: see "Publication," pp. 3-4)

• Notice of Copyright
(USCO: Circular 1, Copyright Basics: see "Notice of Copyright," pp. 4-5)

• Duration of Copyright
(USCO: Circular 15a: Duration of Copyright)

• Extension of Copyright Terms
(USCO: Circular 15t: Extension of Copyright Terms)

• When Works Pass Into the Public Domain
(Laura Gasaway, University of North Carolina)

• Copyright Term and the Public Domain in the United States
(Cornell University)(USCO: Circular 15: Duration of Copyright)