Wants to Copyright Public Domain Photos

Mrs. Tibitts (circa 1860)

Dear Rich: I am starting a small business and I want to use some old photos (pre-1923) on my packaging. Two questions:(1) If I purchase a pre-1923 photo and it becomes my physical property, can I copyright the image (even though I didn’t take the picture)? (Essentially, if I am going to print out a bunch of packaging with this image, can I protect it?) (2) I Google-imaged some specific search criteria and several images that I would like to use for my packaging came up. When I clicked on the images I would usually end up on a blog or Flickr. Let’s say the image in question was taken pre-1923 and it is on a person’s blog. Can I still use that image for my packaging? Short answers: (1) No. (2) Yes.
Longer answer (1) Once something's fallen in the public domain as a result of old age (as has all photography published in the U.S. before 1923), it cannot be reclaimed. If you modify a public domain work --  add additional imagery, unique coloration, or anything else arty -- you can claim your combination of old and new. But you will never be able to stop someone from reproducing the underlying public domain image with one possible exception. If you use a public domain image as your product's trademark, you may be able to stop competitors from using the same image on similar goods under trademark law.
Longer answer (2) It doesn't matter if someone "discovers" a public domain work and publishes it at their blog. If it's public domain, anyone can reproduce it. For more on the public domain, check out Steve Fishman's excellent book.