I find the following in the census recors for 1910 and 1920. In the 1910 census original images Carl Nilsson's middle initial looks more like a J than an F.

1910 United States Federal Census
about Carl F Nilsson
Name: Carl F Nilsson
[Carl J Nilsson]
Age in 1910: 43
Estimated Birth Year: abt 1867
Birthplace: Sweden
Relation to Head-of-house: Head
Father's Birth Place: Sweden
Mother's Birth Place: Sweden
Spouse's name: Anna M
Home in 1910: Chicago Ward 25, Cook, Illinois
Marital Status: Married
Race: White
Gender: Male
Year of Immigration: 1899
Neighbors: View others on page
Household Members: Name Age
Carl F Nilsson 43
Anna M Nilsson 39
Carl S Nilsson 12
John E Nilsson 11
Gurlie M Nilsson 8
Ermi S Nilsson 3








1920 United States Federal Census
about Carl J Nilsson
Name: Carl J Nilsson
Home in 1920: Chicago Ward 33, Cook (Chicago), Illinois
Age: 52 years
Estimated Birth Year: abt 1868
Birthplace: Sweden
Relation to Head-of-house: Head
Spouse's name: Anna M
Father's Birth Place: Sweden
Mother's Birth Place: Sweden
Marital Status: Married
Race: White
Sex: Male
Home owned: Rent
Able to read: Yes
Able to Write: Yes
Image: 1032
Neighbors: View others on page
Household Members: Name Age
Carl J Nilsson 52
Anna M Nilsson 48
Carl G Nilsson 22
Eric J Nilsson 20
Gurli M Nilsson 18
Irma M Nilsson 13

I don't find any Nilsson's in Freeport in either of these census records.

In 1930 there is an Anna M Nilsson living as a boarder in Chicago.

The Illinois Death Index has death records for:

Anna M Nilsson 04.20.1934
Carl Nilsson 08.28.1940

Both died in Cook County.

I don't know if this will help you at all as they are not in Freeport.