I've read that they were planted extensively as "living fences" until the guy that invented barbed wire came along. They can be spread easily, and do not necessarily have to be planted - cows, squirrels, ect. will eat and distribute the seeds.
I don't think as far back as 1700, though. Any old farmland areas that have not been developed will have them. Here in Shenandoah county, they are very common, many still in long, kinda straight rows showing old property or field divisions. They plowed HUNDREDS out between the lanes on Rt 81 by Strasburg last year