Actually, on three occasions (in 1868, 1869, and 1873), Rosario was declared the federal capital by the Argentine government, only for the president to veto it each time. In fact, to this day, the main newspaper in Rosario is known as La Capital.
In addition, some small towns in that general part of Argentina (or heading from there towards the city of Cordoba) were considered around that time for that purpose but ultimately rejected. These include Fraile Muerto (present-day Bell Ville, just inside Cordoba Prov.) and Villa Maria (somewhat deeper inside Cordoba Prov., and declared as federal capital in 1871 by the government before being vetoed by the president).
Just wondering: If Rosario were the federal capital to this day, would that have more likely prevented it from being the present-day leading drug/gang city in Argentina? And/or would have caused Juan Galiffi (1892-1943; the Al Capone of Argentina) to locate his mafia-type activities somewhere else and make that other place the "Argentine Chicago"? And I would imagine that Rosario, as the federal capital, would still be a major industrial, trans-shipment, and port city (albeit perhaps relocating those functions further away from the city centre, at least over time) owing to its location in Argentina?