Can a photo taken from public domain be modified?

Question

I want to make a Prairie Schooner the Background Image on the profiles of the people in the Keeney Wagon Train. I found one, but the sky is superfluous & it needs cropping to show the wagon better. It also has to be made smaller. Does anyone have any suggestions? It's on Burkhalter-179, Keeney-576 & some others now. Thank you.

Answer 1

Yes you can use the image freely and manipulate the picture to your liking.