The East Washington was the vestigal remnant of the old Chesapeake Beach Railway which gave up the ghost on April 15, 1935. The East Washington survived for another 40 years or so on a slim diet of a liquor company needing deliveries by rail and mostly delivering coal by rail to the local power company from the place locally as known Chesapeake Jct, the interchange with the B&O near the intersection of Deane Ave. (now Nanny Helen Burroughs Ave.) and Minnesota Ave., SE. When the nearby power plant converted to oil, that ended the sole reason for the continued existence of the E-W and they abandoned all operations in the latter 1970's.
There is an excellent hardback book out on the whole subject of the Chesapeake Beach and the East-Washington Railway by Ames Williams and is currently available NEW for $20 or so and is available from the Chesapeake Beach Rwy Museum in Chesapeake Beach, MD.
As for the right-of-way ... the Chesapeake Beach line is visible for much of the 28 miles or so in Maryland and the Chesapeake Beach Rwy Museum organizes a hike each year for a portion of the r-o-w, weather permitting around the first weekend in April. Inside the DC line it is more built up and IF you know where to look and and do not mind a less than desirable neighborhood and do NOT get out of your car while exploring, those 3 miles are at least partially findable. Having the book in hand helps though.