like this) is more likely to be protected than a minimalist creation (like this). If you're highly risk-averse, stay away from reproductions of decorative post-1922 iron work (and post-1922 iron work photos, for example from this book).
Copyright and iron works. Although blacksmiths may possess skill and craftsmanship, designs included within functional objects (such as iron work) will be protected “only if, and only to the extent that, such design incorporates pictorial, graphic, or sculptural features that can be identified separately from, and are capable of existing independently of, the utilitarian aspects of the article.” (Here's an explanation of the rules and this case illustrates how the standard is applied to belt buckles.) Iron work is also difficult to protect because it often lacks sufficient originality – that is, it's comprised of generic shapes of twisted iron. The issue can get more confusing when the iron work is incorporated within the architecture of a post-1990 building (or when the blacksmith claims copyright of his creations). Of course, iron work created prior to 1923 is probably in the public domain.
PS Dept. You mentioned the iron work of Charles Simmons but we wonder if you mean Phillip Simmons (unless you're referring to Phillip's nephew, Carlton).