That would've been the Union Pacific bridge, which lasted into the 80s: https://bridgehunter.com/wa/pierce/bh55394/
I believe that your info on this bridge is not correct. I live in Tacoma Wa where this bridge was located. You say that it was no longer used after 1973 (when it was removed).
I did not receive a drivers license until I was 16 years old in Dec. 1975, and I can remember using that bridge as a short cut across the waterway to beat traffic on the 11th street bridge near by I used this bridge all the way through high school (graduated in 1978). So I can personally verify, from personal experience, that it was in use through 1978.
It was a swing bridge that I thought un usual, as it had the railroad track down the center, and the traffic lanes outboard so the lanes were split by the R/R track....
Greg, your image is also related to the UP bridge, not of this one.