This is not sensible. 57 minutes for two separate tickets puts you at real risk, particularly where the second ticket is an award. I would not advise this even if it were a connection. But, it's not a connection.

UA requires that you be at the departure gate no later than T-30. If the flight is at risk of an oversale, you will have noshowed and will be off-loaded. Theoretically, you have also lost your ticket. But, UA will generally rebook you. However, on an award where you have noshowed -- rather than misconnected -- you may need to wait for the next UA flight with award availability or at least standby.

You will likely be able to obtain your BP at SMF, but if you can't, you can get it at the gate at ORD.