Bluebulb Projects' The Measure of Things presents:
3,500 is about thirty times the number of Union Stations in the United States
In other words, it's 25.90 times the count of Union Stations in the United States, and the count of Union Stations in the United States is 0.0386 times that amount.
(a.k.a. Union Terminal; a.k.a. Joint Station; a.k.a. Union Depot) (2016 figures)