Bloodroot is native to eastern North America from about North Dakota and Oklahoma eastwards in both Canada and the U.S. It is a plant of the woodlands and rocky slopes. Shade is preferred, even quite dense shade. The clump will expand by rhizomes, though never as quickly as you would like. We also see it spread by seed, as we find new plants 20 or 30 feet away, across a pond where rhizomes couldn't go. Bloodroot is not all that picky on location, but prefers a leafy soil, slightly acid. Some books say that it will also grow in sun. I expect that is in the northern parts of its range, and not in the southern areas.
Although it is harder to find, you really need to have one of the double form, Sanguinaria canadensis 'Plena'. The flowers remind me of a tiny magnolia blossom. It seems to come up and bloom a little later than the single form, but it may just be because it is in a slightly cooler and shadier place than the others.
I wish I had a picture of the bank across from our farm in Berks County Pennsylvania. Not sure why I never took one. Three kids under the age of 5 might be part of it. Anyway, at the intersection, on one corner there was a steep bank, maybe 6 or 8 feet tall and 20 or 30 feet long, totally covered in Bloodroot. Just gorgeous. I've never seen anything like it since. Even our hillside of Trilliums doesn't have quite the impact of that spot. I often wonder, in the spring, when I look at our tiny Bloodroot patches, if it's still there or it someone, in the interest of 'improvement' thought they should flatten out the bank for a driveway or something else. It would be a shame. I hope it's still there and someone else is enjoying it as much as I did.