This is from the November 22 FEBT Newsletter:
On October 8, 2022, the joint EBTF-FEBT archive project reached a major milestone: the online launch of a rich collection of publicly-available historical material. It is available here. The EBT Foundation holds a treasure-trove of materials reaching back to the 1860s: over a thousand maps and plans, shelves of bound volumes, many hundreds of photos. Combined with the hundreds of historic photos held by the Friends of the EBT, these are the makings for a major railroad archive.
Archives link:
https://ebtfoundation.org/archives/
Just in case its not clear, EBTF is the East Broadtop Railroad [Foundation] in Pennsylvania and the FEBT is their "Friends of the East Broadtop" volunteer/support group.