Well, just in case you haven't reviewed the wiki entry on Columbus Union Station
The freight yards and servicing facilities located east of the station had been replaced by the construction of the new Buckeye Yard near Hilliard by the Penn Central in the late 1960s. The multitrack yards and shop areas eventually gave way to I-670 in the early 1990s. The viaduct over I-670 was constructed with a cap, and shops lining High Street reminiscent of the long gone arcade.
Union Station was closed in 1977 due to lack of usage, and the station torn down and land repurposed, at least partly for the convention center. Remember also that union stations from the peak era would have a lot of servicing facilities and supporting trackage - coach yards, express/mail, LCL freight, and so on. That all dwindled away thru the '60s and '70s till no longer needed.
So, not an unheard of story for many mid-tier US cities...