One of the last two foot gauge to carry passenger was the Fort Dix Railroad at the Army Camp in central New Jersey. This was not revenue passengers but was after the closing date of the lines in Maine. Also, the last may have been the Baby Gauge RR that connected to the Death Valley RR in CA. I was a mining line that changed to a tourist operation having big cushion seats on track car size vehicles that went through tunnels and over various trestles. And, its track is still all there just like the East Broad Top, with tunnels caved in. Ran into the 1960s I believe. PRR