The East Broad Top Railroad (EBT) is a 3 ft narrow gauge historic and heritage railroad headquartered in Rockhill Furnace, Pennsylvania.
Operating from 1871 to 1956, it is one of the nation's oldest and best-preserved narrow-gauge railroads, and was designated a National Historic Landmark in 1964. The railroad is now preserved for use as a tourist attraction. After a nine-year closure, in February 2020 it was announced that the railroad had been purchased by a non-profit foundation and regular train service resumed in the summer of 2021.
There is significant coverage of the railroad elsewhere on the internet, so I am not going to replicate it here. Below are a few links that may be of interest to you...