Axolotl described the last mile. I would suggest that when you are about 2.5 miles out from Georgetown watch for the National Capitol Trail to come in about ten feet on your right (at Fletcher's Boat Yard) and switch to that nice paved MUP. It parallels the C&O into Georgetown and will dump you on K street which runs underneath the Whitehurst Freeway. Follow K about 1 mile to get on the Rock Creek trail. WHere the main K street road goes up you will go right under the bridge -- follow the car entrance to Rock Creek Parkway and then turn left at the MUP.