This trolley is Toronto Transit Commission #4603. It was built in 1951 of components manufactured in St. Louis and Montreal, assembled in Montreal, and delivered to Toronto. It was completely overhauled in 1984 and continued to run in Toronto until 1995. It was one of the last Presidents' Conference Committee (PCC) type streetcars built in North America. (The PPC design was agreed upon by a group of the presidents of the transit companies, not the U.S. Presidents, to be a standard design and was then duplicated for most of the trolley companies in North America.) Until the 1950's you could see this streetcar (in various colors) in just about every major city in the U.S. and many Canadian cities. (My understanding is that Toronto still runs a trolley system.)
The NCTM has one of the trolleys actually used in DC but, not ever having been overhauled it's not nearly in as good a condition as this one. So the only streetcar running in the U.S. Capitol area is a Canadian one.