this is a more complicated question because it is also a matter of how iron is absorbed from the food source. Sources from meat, fish and poultry are more readily absorbed than from fruit and vegetable sources, and even the preparation can make a difference.
There is an excellent article from the University of Illinois that gives a lot of detail about it including Recommended Dietary Allowances (RDS) broken down also for vegetarians and vegans. Here is the link to this source: http://www.mckinley.illinois.edu/handouts/dietary_sources_iron.html
For further information on a few meats and their iron content, visit this website http://www.bisoncentral.com/cooking-bison/nutrition-information
Bison is a very lean meat that is naturally high in iron. Most bison, to my knowledge, are never fed antibiotics or steroids. It should say so on the label.
Also, go here for some general information on the top 10 iron-rich foods.