How about planting "hedge", also known as osage. Makes a great barrier/border with the added benefit of growing the best bow wood in north america!
Sorry, I should have been more specific. All that grows here in my part of TN is hardwood trees and cedar trees and unfortunately Im allergic to the cedars. I am on The Upper Cumberland Plateau.Ah, didn't know you wanted native plants. In that case I would look into any native pines or cedars, that will give you evergreen coverage and a fast growth to a decent masking height. Some pines do well on poor soils as well.
Actually, I am planning to buy some razor wire and store it for an emergency. A neighbor and myself are planning to plant something along our road for privacy and security. Other than cedars there are not any native evergreen trees in my area. Firs are pretty but they don't do good at lower elevations in my part of TN, they need to be planted above 2000 ft and I am at 1100ft elevation. They do good 2 hours east of here because of the elevation increase.If your rural, the point is to have "natural" cover... neither of these are native to the area, so you're going to stick out like a sore thumb. I would go with something else myself. There are many other evergreen options other than Cedar. There are several variety of firs that grow extremely fast. Heck, you could always put barbwire/razorwire in the lower branches on short notice if something where to happen.