Narrow gauge is alive and well at the Orange Empire railway Museum. They have 42" street cars from the Los Angeles Railway.
They also have the Ward Kimball collection as mentioned. The museum has also added some additional ng from one of the local historical museums ie aa box car etc. Also they have rebuilt one of the little single truck cabooses from the Westside Lumber line that was 36"
They are the only museum that I know of that runs on 3 gauges, including that "broad gauge" track at 56 1/2".