My husband's great-great-grandfather was Nicoli/Nicolas/Nichlos PETERSEN, born in Denmark. He married Anna SVENSEN (born in Sweden) in 1876 in Chicago; he was 30, she was 28. We think we've found them in Chicago in the 1880 census, shown with 2 sons, Albert (age 2), and Edward (age 1 month).
My husband's great-grandfather was John Albert PETERSON, born 1878 in Illinois (possibly Cook County). He died in California in 1951; his death certificate shows his father's name as Nichlos PETERSEN from Denmark (with a notation in the margin that the spelling is correct); mother's name Anna, from Sweden.
John Albert married Golda/Goldie Geraldine CLEVER (born 1881 in Canton, OH) in Milwaukee, WI, in 1898. Their marriage license shows his parents as "N. Peterson" and "A. Swanson."
Goldie's parents were William Garrison CLEVER and Alberta "Birdie" SMITH; she had 5 younger brothers. Her family moved from Ohio to the Chicago area sometime between 1893 and 1896.
John and Goldie are shown in the 1910 US census living in Chicago, with 5 children, all born in Illinois; the oldest, Blanche, is already 10 years old. Other children were John Jr. (age 8, my husband's grandfather); Mildred (6); Roy O. (4); and Walter G. (not recorded).
We would welcome any clues or connections.