Pokorney & Mackett

I am looking for sources or ideas on finding information regarding my great grandparents who immigrated to south western Prarie du Chien, Wisconsin from Prague about 1875 . They are James Pokorney born 4 Jul 1857 Rose Mackett born 26 Aug 1862 Other information I would like to better understand is where did Czech people depart from and where did they most likely arrive in the