Nice overview.
Three of these railroads, CSX, Norfolk Southern and FEC come together at the Beaver Street viaduct. It is the northern most track for FEC and the southern most track for NS. Today, I believe they have interchange agreements where each other's trains can run directly into each other's switching yards.
As I recall, ACL was moved here from Wilmington, NC. I think Seaboard was HQ'd in Richmond and Chessie in Baltimore. CSX and NS also split up Conrail, HQ'd in Philadelphia and the successor to Penn Central and other northeastern bankrupt railroads. The Louisville & Nashville (L & N) railroad was another big acquisition. Jax was fortunate to hold on to CSX through all the mergers that created it.
Another major asset at one time for CSX was its ownership of SeaLand, the originator of containerized freight. Most of it was eventually sold to Maersk Lines. And then there was the Greenbriar resort in West Virginia... Congress's secret hideout
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