They came in search of employment, and a better life for their families. Chicago had many opportunities for employment, although much of this employment was hard, dirty jobs like at the stockyards, where there were no laws about workplace safety, or fair labor laws. A good bookto read about this, which included polish and lithuanian immigrants, is The Jungle, by Upton Sinclair.
My great grandfather and grandfather came for the work. There were steel mills and other jobs here. They had family already here to help them get started. The landscape was similar, although it s about one zone colder in Chicago than in Warsaw.