Around 1900 a number of Corporations bought up the small family-owned car building companies. American Locomotive Corporation took over 11 locomotive builders. The American, Car & Foundry took over about 10 car builders.

Did the old names continue to show on builders plates?

We have a Brooks Locomotive Works locomotive from 1909 with both ALCO and Brooks on the plate at the Western Railway Museum.
Did St Charles Car Company passenger cars also say A,C & F on them?

Do the Official Guides to passenger cars show this data?
Thanks,

Ted Miles, retired but still interested in trains.

1910 built Tooele Valley 11 (originally Buffalo and Susquehanna 169) has on its builder's plate American Locomotive Company Brooks Works on it: https://donstrack.smugmug.com/UtahRails ... -T5Kbshr/A

Not all the independent locomotive works that were amalgamated into ALCO remained open. Matt Giardino will know when the individual plants closed. Rogers (large, but crippled by location limitations) was open until 1913; Richmond stayed open until 1927.