When the diesel age began right after WWII, the most popular locomotive was the Electro-Motive Division (EMD) F Series. The F Series locomotives were produced from 1939 to 1960. They were called F Series because the first one, the FT, was fourteen hundred horsepower. The last one, the F9, would be 1,750 hp.
After the FT was introduced in 1939, came the F2 in 1946, then the F3 in 1946. There was a short lived F5, that was a late model F3 with F7 components. Then the F7 came in 1949, then the F9 in 1953 to 1960. All of them were 4-axle locomotives. The F Series was available in two configurations; a cabbed unit, or A unit, and a cabless, or B unit. There was also a passenger version for each one that was 4 feet longer. Each model had Phases that only railfans could point out. For example, one Phase had horizontal slats on the intake grills and the next Phase had vertical slats.
On "Merger Day" in March 1970, BN had a large collection of F units from the four merging roads; NP, GN, CB&Q and SP&S. BN had around 300 cabbed A units and some 220 cabless B units. BN came up with a great re-numbering plan; all cabbed units would be even numbers and the cabless units would have odd numbers. The F3s and F7s were numbered in the 700s, the F9s were numbered in the 800s. Passenger F3s and F7s were in the 9700s, the passenger F9s were in the 9800s.
This seamed pretty straight forward in the beginning, but it didn’t take long for things to unravel. Right after the merger in March, BN started trading in the older F units for SD45s. This opened up a bunch of number vacancies. Then in 1971, Amtrak was born. When Amtrak was created, the freight railroads were required to “hand off” their passenger locomotives. What the freight railroads did was, they handed off the worst-of-the-worst and kept the best locomotives for themselves. Now the 9700s and 9800s that didn’t go to Amtrak, had to be renumbered into the empty spots with the freight locomotives.
If you want to find more on the renumbering of the F units and how BN kept track of them, I suggest the book, Burlington Nothern Railroad Locomotives 1970-1996
by Robert Del Grosso. Robert did a great job putting all the information together, with cross referencing from the merging roads to their new BN road numbers. His book can be found on Amazon
I do not have any photographs of F units in my collection, by the time I got my drivers license the F units were pulled from service. The rise in fuel cost in 1979 and then the ’80-’81 recession, combine with their age, made the F units a prime target. Some were sold for their metal value and some were traded in for new locomotives. All of the photos on this web page are from the collection of Roland Haynes’s. His job as an engineer took him around Western Washington where is was able to take these photos before they disappeared for good.