Subway System History

My interest is in the coming up of the NY rail system [under and over ground]; particularly within the first years. My family worked as drivers on the IRT and I wish to learn as much as I can about what they did, how they did it, why they chose that path. Irish immigrants fleeing their deep connection to the IRA at home; they came to NY in 1911, and started in Manhattan, then moving to Hastings On Hudson in the 1920s. The brothers continued their employment with the IRT their entire careers.

Researching remotely during this time of COVID, I do not know what avenues are available for researching the history of the IRT. I welcome any insight.