Who were the parents of Peter A. May of Chicago?

The May family was found on Ancestry World Tree  

What we knew
Vital Statistics Peter was born about 1909 in Chicago, IL and married Emily about 1934. He died in 1970 in Chicago.
Where we looked
Chicago Tribune 
Peter's 1972 obituary gave the names of his siblings: Peter A. May Sr., husband of the late Emily D., nee Schroeder; father of Walter F., Peter A. and William H. May; brother of Mildred Corcoran, Elsie Legace and the late Mathilda Florian.
1930 census
Using the every-name index for the 1930 Chicago census, we easily found Peter, 22, with his family. His father is listed as Nicholas J. May, widowed. Peter's siblings Mildred and Elsie and a boarder named Michael Corcoran also live in the household. The parents of Nicholas were born in Germany.
1920 census
The same family is in Chicago in 1920. Peter's sister Matilda is listed and the mother is named Elizabeth.
1880 census
Nicholas is a child in the family of Stephen and Josephine May in Du Page County, Illinois in 1880. Both parents are born in Prussia.
Marriage index
The index to the Illinois marriage records includes a marriage between Stephen May and Josephine Ranches, January 10, 1870 in McHenry County.
What we learned
Family Tree Peter's parents were Nicholas May and Elizabeth. The parents of Nicholas were Stephen May and Josephine Ranches.
Where to go next A family tree never ends. We still have to find out more about Stephen May and Josephine Ranches. McHenry county is a good place to look for more information and Du Page county may hold more clues.

We still do not know the maiden name of Peter's mother Elizabeth. She apparently died in Cook County between 1920 and 1930 - a death record can be easily obtained, though not via the Internet!

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