I looked at Mentha arvensis (American Wild Mint), LW, and it's definitely not that. Mint has flowers that whorl about the leaf junctions. The leaves look similar. Actually more similar than prunella vulgaris.
The more I look into this, the more I think it is Prunella. All the write-ups talk about Vulgaris but maybe my problem is that there is another species occuring locally. The descriptions of the way it grows even sounds a lot like this speciman. One article even says, "the more you mow it the shorter it grows". That would fit this to a "t". If not mowed it is supposed to reach 2 feet. I've not seen any that tall before.
If it is "Heal all", there are some interesting articles about its use as a folk medicine. Some give recipes for teas and poultices. Some say there are benifits derived from chewing the leaves. It is supposed to have been used to stop bleeding from open wounds and could interfere with prescribed blood thinning medicines.
An interesting plant.
I anxiosly await input from you folks to see if I shouldn't consider it Identified. :-/