St. Paul Union DepotSt. Paul Union Depot was among the busiest and best known places in the cityone of the largest depots in the nation and St. Pauls link to the world. It had nine platforms, twenty one tracks, and well over 140 trains coming and going each day. At its peak in the 1920s, the Union Depot processed more than twenty million pieces of mail each year. Construction of the new depot began in 1917, among the burned remains of the previous depot, and was finally