My grandfather was also named John Swiatkowski although he was born about 1872 and came to the United States in 1876 with his parents (Franz) and 4 siblings. Grandpa died in 1948 in Posen, MI. They originally came via New York to Detroit and lived there until about 1890 when they bought land in Posen. The family had relatives in Wisconsin near or in Milwaukee where my uncle stayed while learning the carpentry trade in the late 40's. He of course doesn't remember how he was related. I had found a Constantin Swiatkowski in Wisconsin in the 1870's but do not know if this would have been your relatives. I believe I found them on a 1870 or 1880 census report.