If you can find a wild blackberry vine that produces good fruit this is what you do. You trace that vine back to where it goes in the ground. Mark that cane with a wire tie or bread bag tie and then leave it. When the foliage dies back go back to the area where the marked vine is and using a chopper of some sort whack the vines down. Find that one you marked and dig up the roots. Bring the roots home and cut the largest roots into 4" to 6" pieces. Bury them in damp sand and keep them from freezing. Around February dig up and till in the area where you want the blackberries to grow, Add lots of compost and organic material. Plant the vine roots in trenches about 3" deep and copver with soil tamping it down to make it firm. The blackberries will grow and be the same ones you had last year.
Now this is how people have been collecting wild vines since the Dark Ages according to historians. It is a tried and true method of collecting wild vines. But like Chuck and Tut said, the wild vines are a far cry from the Hybrid thornless and other varieties today. I grow Arapaho thornless berries and they produce a very high quality berry in large quantities without much care. I choose to prune mine according to methods developed at the University that developed the berries but you don't have to. I grow two plants on a raised hill 8' long and 4' wide 20" high. I get enough berries from those two plants for me and Nancy for cobblers, muffins and a small amount of preserves. I am expanding to 6 bushes next year.
Another way to propagate berries is to use what is called air layering. Cut a slit about half way through a good cane maybe 2 feet from it's end. Open the crack up a small bit and stick part of a toothpick in it to hold it open. Wrap a plastic bag with filled with wet peat moss around the stem where cut and then seal it with more plastic and tape. The bag should be about as large as a softball. Keep the peat moss damp all the time. After a few weeks there will be roots in that bag attached to the end of the vine. Cut the cane about 1" on the plant side of the bag and you have a separate plant. A good plant can provide quite a few of these air layered cuttings in a year. Pot it or plant it in the ground. BTW, technically this is illegal to propagate a patented plant. Just FYI.
BTW this air layering works with grapes, muscadines, and almost any vines there is in addition to some plants.