The C&O Canal runs 184.5 miles from Georgetown in Washington to Cumberland, Maryland. DC Audubon sponsors an annual bird survey of the canal each January. A little over four miles of the canal run through Northwest D.C. The best access points for birding the canal in the District are at Fletcher's Boathouse in Mile 3 and the Chain Bridge in Mile 4. Many great birding spots are farther up the canal in Montgomery County, Maryland, including the Little Falls Dam, Great Falls, Pennyfield Lock, Violette's Lock, and Sycamore Landing. Fletcher's Boathouse has access to the towpath as well as views of the river. At the Chain Bridge, there are a series of ponds in the rock formations below the bridge. You can view these from the bridge's pedestrian walkway. The boundary between Maryland and DC is approximately a half mile north of the Chain Bridge, near the mouth of Little Falls. Use caution when walking the canal on weekends as the miles closest to Washington are used heavily by cyclists.