Yes. The copyright belongs to you, or your heirs in the event of your death.
This is called work-for-hire and copyright generally belongs to your employer.
Yes. Copyright generally belongs to you as the artist rather than the purchaser of the work.
Authors of joint works are co-owners of the copyright.
Ownership of the physical item is not synonymous with ownership of copyright. If you own the physical object, but not the copyright, you can transfer only physical ownership to the archive. Copyright remains with the original creator, unless he/she transferred those rights in writing.
Ownership of copyright must be expressly transferred in writing through a deed of gift.
You jointly own the copyright with other heirs, regardless of who possesses the physical materials. U.S. copyright law specifies that any of the joint copyright holders may authorize the nonexclusive reproduction, distribution, performance, and/or modification of the work.
Photos: If you took a picture with your camera and the concept was your own, you are the copyright holder. If you were given a photograph, but did not create it, you own the physical photograph, but not the copyright.
Letters: The recipient of the letter has ownership of the physical letter, but the letter writer (the creator) owns the copyright.
All unpublished works: Works created before January 1, 1978 that have not been published are protected for the life of the author + 70 years. Any unpublished work whose author died more than 70 years ago entered the public domain on January 1, 2003.
Audio-visual works: Copyright is generally shared by the ‘makers’ of the recording, i.e. the person or organization who owns the recording equipment and produced the recording, and the person(s) who generated the content captured on the recording.
Interviews: The interviewer and the interviewee are generally co-owners of the copyright.