I seems that STEVENS was not Agnes' maiden name.This is an entry from the 1930 census for Linn, Walworth Co, WI: STEVENS, Paul age 37 b. WI, father b. NY, mother b. WI wife Agnes age 23 b. WI, both parents b. WI dau Betty June age 0 b. WI stepdau HALEY, Phyllis age 5 b. WI, both parents b. WI
1940 census for Lake Geneva, Walworth Co, WI: STEVENS, Paul age 47 b. WI wife Agnes age 32 b. WI dau Phyllis age 15 b. WI dau Betty June age 10 b. WI
It looks like Paul STEVENS was Paul Millard STEVENS b. 6-Aug-1892 in Manning, Vernon, WI to John Townsend STEVENS and Agnes Lucretia HEBARD.
Paul Millard STEVENS 6-Aug-1891 to 4-Feb-1983 and Agnes Irene STEVENS 17-Feb-1907 to 21-Apr-1994, are both buried in Hustisford Cemetery, Hustisford, Dodge Co, WI.
I saw Phyllis' obituary while researching.It says she is survived by her sister, Betty LEITSKE.
There's an 85 yr old Betty J. LEITZKE living in Hustisford, WI.If you could contact her, she might be your best source for information about her mother.
There's a mention of Agnes STEVENS in the 23-Jan-1965 edition of the Janesville Daily Gazette at newspapers.comSince it is a pay subscription site, I can not view itHowever the bit you can see on a google search says "a daughter, Agnes Stevens of Hustisford, 6 grandchildren and 15 great grandchildren"It looks to me like it might be an obituary for one of Agnes' parents, which would tell you what her maiden name was.