Source: http://criswellphotography.com/tag/railroad-cut/
Not citing the source of photos is plagiarism. Here is a post on why this is bad, and here is how easy it is to find allowed photos.
Not indicating that the content you copy/paste is not your original works could be seen as plagiarism.
Please refrain from using #photography for posting art, posting graphics, posting other users photos without commentary, etc. Abusing tags can potentially lead to people flagging you, even from dan himself.
#steemitphotochallenge is used by a specific type of content. You can find information here for the Steemit Photo Challenge
Thank You! ☙