Philadelphia, which you left out, also had a large system that lasted late. SEPTA which runs the system still tries to get ride of streetcars and trolley buses even today. Most of the lines left use the downtown subway. The surface lines have been abandoned one by one until there may be just one left. They still have three or four trolley bus lines also.
Actually Philly restored the #15 surface line to service I believe 3 years ago, might have been 2. They even rebuilt the PCC cars adding lifts and AC to the cars for that line.
And having restored the #15, that brings the number of surface trolley lines up to six. I believe the Elmwood Ave (36), Woodward Ave (11), Chester Ave (13), Baltimore Ave (34), and Lancaster Ave (10) trolleys have all operated continuously. The Girard Ave line (15) was restored to trolley service after about fifteen years of being a bus.
The full infrastructure remains for the #23 as well -- at one time the longest urban streetcar line in the world, extending all the way from Chestnut Hill to South Philly. All the track and wires are still in place... though restoration of trolley service seems highly unlikely.
And a new line, which will be the seventh in operation, is in the planning stage. This will be a trolley along Philadelphia's waterfront using existing Columbus Ave tracks and running on new tracks down Market St from the waterfront to City Hall and the Convention Center, with possible future extensions south to the Navy Yard or Phillies/Eagles stadiums.
Also, don't forget our two former Red Arrow suburban trolleys, to Media and Sharon Hill, and our former Philadelphia & Western trolley to Norristown, all running continuously for approximately a century. Of all the lines mentioned, only the Norristown line runs third-rail; all others are catenary.
This is peanuts compared to what we once had.
PTC track map, 1954. But it's probably more continuously operated surface catenary/trolley lines than any other American city.