Polish immigrants from the German occupied regions of Poland were arriving in Chicago in greater numbers during the 1860s. Some of them joined the German parish of St. Boniface because the Poles had no church of their own in 1865. St. Boniface was founded in 1865 in the West Town neighborhood of Chicago. The Polish parish of St. Stanislaus Kostka was founded in 1869 and most of the Poles became members there. The indexed portion of St. Boniface records includes only the years of 1865-1870 when the Poles were more likely included. Some of the Polish names were badly mangled and corrected when evidence from other sources warranted it.
One occasionally finds "Polish" names in St. Boniface records after 1870. These may be people who identified more closely with German culture or intermarried with them. It may also have been a convenience-- if you lived next door to the church, going there would be easier than walking several blocks to the Polish church!
The marriage records start out in 1865 complete with names of parents and where the bride's and groom's were from. Part way into 1867, that additional information was no longer included.