Seeking info on my Pokorny ancestors' arrival in America (c. 1854), early family records (1860s/Chicago, IL?)

At least some of my Pokorny ancestors were living in Chicago in the 1860s. I know the children’s names (Elisabeth or Lizzie, Ellie, Annie & Mary, my great grandmother, who married Paul Wilhelm Ludwig Ziemsen) but not their parents’ names. These, based on internal family evidence—recurring names among their grandchildren—may have been Frank (Franz? Frantisek?) and Maria or Elisabeth.

I believe they were related to John Pokorny, a woodcarver & furniture maker who was living in Chicago in the late 19th and early 20th centuries.

See my Surnames statement for more details, dates, marriages.

I have been unable to find any record of this family (except for Mary Ziemsen and Elisabeth Pokorny Maas and possibly John) in any U.S. Census or other accessible documents.

I would love to know when they arrived in America (probably c. 1854) and from what city or town in Bohemia they hailed. Also what became of the rest of my great grandmother Mary’s siblings.