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Centuries for sure. I know it as a NE woodland/forest floor plant, I don't know how far into the southwest it goes. You can buy it as a flowering ornamental too. I've got a shady spot near my house and one day I hope to put in a bunch of native plants as a gesture to what was once here (I'm trapped in the burbs for the time being), and bloodroot would be one thing I'd try.
I own a compendium of herbs the Shakers used that I picked up years ago in a used book store (published in 1976, Amy Bess Miller). They were taught by the natives so it's passed down info, and bloodroot is listed as you'd expect:
"Valuable in typhoid pneumonia, catarrh, scarlatina, jaundice [!], dyspepsia, ringworm, and in affections of the respiratory organs. In small doses, it stimulates the digestive organs, acting as a stimulant and tonic. It appears to be used chiefly as an expectorant."