If you are traveling for the 4th or anytime this summer and don't have a GPS unit like Garmin or Tom-Tom, here is something that rivals those that you can get at no cost and works great on your smart phone. I've been using it for quite awhile on my iPhone and it keeps getting better. On a recent trip to San Francisco, it routed me all over the city and avoided traffic problems with ease.
I found that by applying a Velcro strip on the dashboard where the phone could be seen and then placing a strip on the back of the phone... or getting an inexpensive plastic case from the Apple store on which the other piece of Velcro can be attached, you have an effective navigation screen. This app also has voice directions and is very good at prompting for turns. I found that keeping the phone plugged into the car's power port/cigarette lighter is a good idea since the phone uses quite a bit of power to run this app.
Happy traveling.