Rivnuts from Homestead,PA on 5/4/2024 7:52:49 PM:
It is quite doable. From Reagan Airport, you can ride the Mt. Vernon bike trail north then crossing eastward across the Potomac River via the Roosevelt Memorial Bridge. Once across the bridge you’ll pickup the Rock Creek Trail or on to Virginia Avenue to the Thompson Boat/Rowing center behind which is Mile Post 0 and the origin of the C&O Towpath.
You can follow these trails using Google Maps. Expand it as necessary to see the details supplemented by closeups using satellite view to see the land marks in route.