Please help on these 5 U.S. carte de visite , if one of them is important or of a good value

Colfax, Grass valley, and Auburn were all well known gold mining towns in the 19th century.
That's all I have.
Mikey

 

Agree. Those from Northern California -- Colfax, Auburn and Grass Valley -- are pretty early for the state. There may be some interest, especially for the fellow in Western dress.

Debora

 

The one that is from New York is by the famous photographer Napoleon Sarony. He took pictures of celebrities, but also many photos of people who were not famous. The name written on the back appears to say "Mr Dunning." I have not found any notable man with that name in the early 1870s. More research could be done. As a photo of an unknown person it would be of low value, and the most interest would be in the photographer's imprint. However, there is no shortage of Sarony photos available via eBay and other sites, so even that may not bring much interest.

 

Colfax was also a huge railroad hub at the time .Colfax was the western terminus and supply depot of the first Transcontinental Railroad for many years.

 

" I have not found any notable man with that name in the early 1870s. More research could be done"
Thank you sir, Would you please let me know how to research for that old photographs and old names .

 

I looked in a book that I own that lists actors from the 19th century. I also searched through Google for "famous people named dunning." This search did find a Wikipedia listing for that surname: https://en.wikipedia.org/wiki/Dunning_(surname)
I looked at all of the men on that list who might have been young adults in 1871. However, none of them resembled the man in your CDV.

I also knew of a British actress named Alice Dunning Lingard, who came to the United States. I searched for biographical information to see whether she had a brother. There were no results that indicated that she did.

This is all that I did. More research could be done, but it is time consuming. It may not be worth your time to do it, unless you are interested in searching. It is difficult because you would be starting only with a surname and the name of the photographer and also the place: New York City.