Chicken wire is best for containing chickens - not keeping predators out. No matter where you live, there are more predators than you think, and once you have chickens, they will find you. Even domestic dogs are quite happy to eat pet chickens, and very capable of tearing through chicken wire. I recently moved from a city where I lived 2 miles from downtown. I regularly saw opossums and raccoons lying dead on the side of the road after being hit by cars, only blocks from my house. I'm guessing MD has its fair share of similar inhabitants, and just because you don't see them often, doesn't mean they are not there.
If you are really trying to cut costs, you can do chicken wire, but reinforce the bottom 18" to 2' with 1/2 hardware cloth. That will help keep some of the risk to a minimum.