What is a document that was produced during the same time period as the historical event?

That would be a primary source, It's a document that was was made during the time being studied. Meaning it was written during the time period it talks about

a.   it resulted in widespread unemployment.

the second significant cause of the great migration was the desire of black southerners to escape segregation, known euphemistically as jim crow. rural african american southerners believed that segregation - and racism and prejudice against blacks - was significantly less intense in the north.