Good Lord, I'm forgetting important information...
Henry J. Prang - was born in Illinois- occupation Farmer. His parents are both listed on the 1910 Census as having been born in Germany.
Ada and Arthur are both listed as being born in Iowa.
The 1910 Census has them listed as living in Alsip, Illinois, next door to Emma's parents John and Louise/Louisa Jorn.Since Arthur was born in Iowa in 1909 and the 1910 census was taken in April of 1910, they had to have recently moved to Illinois from Iowas at the time.
If I can be of further help, please email me at firstname.lastname@example.org.