Racephoto,
Our chart coverage is based on NOAA ENC coverage and unfortunately, they have not published ENC charts for the Potomac yet. The current ENC catalog stands at ~630 charts of the ~1000 traditional Raster (paper) charts. NOAA is continuing to make chart conversions - so far this year at about 2-3 per month. As NOAA adds charts, we add them to EarthNC.
The latest Boat US magazine had a good article about the state of charting. Besides the backlog in conversions, they also point out that over 40% of the current coastline surveys pre-date 1960 and some of the depth soundings go back as far as 1940.
As of our August update, it looks like NOAA has completed the Hudson as from New York City to Albany. My hope is that the Potomac, Ft Myers area, and Panama City are soon to follow.
One advantage of using Google Earth in conjunction with the chart data is that the imagery is mostly within the last 4 years, giving a good backdrop to compare the shoreline data to.