Penn Central

[Triplex]

I was under the impression that F-units were mostly gone by the early 1970s.

SP and UP retired their last around 1972, but many railroads had Fs past then. CB&Q had retired all Fs by the BN merger, but GN and NP contributed many, some of which lasted to 1982. Can't remember when Frisco retired their last, but none of theirs made it to BN. Santa Fe's CF7 program ran to 1978. WP's last Fs, IIRC, were retired with the UP merger in 1982. MP's were gone by then. MKT's survived to the late 70s, except one rebuilt unit that made it to the UP merger in 1989. N&W's ex-Wabash Fs and ICG's ex-GM&O Fs survived to the late 1970s. I've seen pictures of B&O Fs as late as 1975 and WM to at least 1978, though none received Chessie paint. Can't remember for C&O. Except their business train, I don't recall Fs in Family Lines or Seaboard paint, so maybe those went early. I want to say 1981 for Clinchfield, though. CNW Fs lasted to 1985, KCS and Alaska to 1986. A number of passenger (mainly commuter) and smaller railroads ran them longer.
In Canada, mass retirement of Fs came later. CN and CP both contributed Fs to VIA in 1978. The Fs remaining in freight service on those railroads lasted to 1983 on CP and 1989 on CN (though I've seen very few photos of CN Fs in service after 1986; they appear to have been stored most of the time after about 1985). VIA's unrebuilt Fs lasted into the 90s, and some rebuilt units to 2002. Ontario Northland's last few rebuilds survived to 2004.