Back before I retired (which was -- sigh -- 20 years ago), "Traffic World" was by far the best single source. Basically this was (maybe still is) a publication for professionals in the business of buying and selling transportation, and it covered in minute detail the actions of the ICC, other government agencies, and carriers that related to the interests of its readers. It has been published for many years, so it's an excellent historic resource.
The down side, though, is that it was/is a weekly publication, so any research on abandonments requires combing through a massive number of magazines. There are also some cautions, since abandonment applications were often denied, withdrawn, or changed, and even when approved, may not have been effected on or near the date shown.