I have looked through a few of my books relating to the period (1850) and I haven't come up with anything as conclusive as I'd liked to have. The Black Ball packets carried passeners also. So it appears that the East River piers served both cargo and passengers. As far as why use the North River it is my understanding that piers were established on the North River because it was deeper. The East River had the preferred conditions for docking and the original docks were established there. But as steamships were bigger and needed deeper slips things moved to the North River. However I have found no confirming reference that the SS United States was actually docked on the North River. However, in checking an 1860 map of Manhattan I have found a solitary North River slip labeled "Liverpool". Unfortunately, more then that I cannot offer. Jim Maguire [log in to unmask]