I'll weigh in a skosh on this:
As Dave and Notchy Bob have pointed out neither the corn nor the milling process was the same as we use now. The photograph shows a mill that is within driving distance of my house and of which I was once (abt 35 years ago) a member of the then Interpretive Society. This mill is restored and used for educational purposes only, but it was originally built in 1846, which is outside the general era of this discussion, but basically the only things that changed were the levels of technology.
I never had anything to do with the milling, so some of this may not be 100% correct as I am using my memory only, This is unintentional and please forgive me and post corrections if I am. In this posed photo we see the miller and some random kid he is instructing siting on the skirt of the mill stone.
The corn being used is what I have always called field corn so I guess that would be Dent Corn. They are picking the black bits you see in the corn pile out of it. These would be rocks, shucks, stems etc. and would decrease the quality of the meal and shorten the stones life. The top stone can be seen behind the lad held in it's lewis. Also note the cornmeal spread out from the seed pile, one can see how much coarser the product is when compared with the previous posted pictures. This is finished meal spread on the stone to lubricate it and to start the flow of milled meal to the edge of the stones where it will fall into a hopper which then allows it to run into a bag (if I remember correctly).
After the initial pile is cleaned, the water wheel will be engaged and the miller will start the mechanism that lifts the lewis and stone up and then lower it onto the spindle protruding from the bottom stone, the lewis is then removed and the drive shaft is connected to the spindle protruding from the top stone. The drive is then engaged and worked up to a grinding speed. The miller can also adjust the amount of the top stone that contacts the bottom. Still it is easy to see just how coarse the finished product is. So to approximate this kind of meal, look for coarse ground corn meal or, if it is just to rough for you, a medium.
The Interpretive Association used to sell up to 5 pound bags of the ground meals and flours to raise money to keep this functioning, then the Great Golden Demokratic Peoples Nanny State of Kalifornia decided you can't sell anything processed by or stored in porous materials (which is why we can't buy Platte Valley Corn Whiskey in the clay bottle here) and that ended. Used to sell them in 1 pound bags for awhile for "educational and decorative purposes" don't know if they still do. And yes, this kind of idiotic fecal mater are just a few reasons I am Mad Michael.