What is your source for the information that Alfred Adelbert married Maedella McKnight in/near Superior, Wisconsin circa 1919? Elsewhere you've posted that they were married in Wausau (Marathon County). In 1919 they were listed in the Waco, Texas, City Directory, and Maedella and their son, Alfred J., both were born in Texas. It seems possible --perhaps even likely-- that Alfred and Maedella met and were married in Texas. Maedella already was working as a teacher in/near Waco in 1916, and already resided at 1700 Herring av., where she and Alfred lived in 1919 acc'd'g to the City Directory and to their son's birth certificate. Maedella lived at that 1700 Herring av address as early as 1913, when she was a student.
If you haven't already done so, I highly recommend that you try to locate an obituary and will/probate file for Arthur E. SKINNER, to see whether those 1939 documents indicate the whereabouts of his son Alfred. If necessary, also track down obits for Alfred's siblings and half-siblings, to see whether any of them mention him as a survivor, or as having predeceased them.
In the meantime, below is a chronological list of some facts you provided and some sources I located. Good luck with your research.
c1894 Alfred Adelbert Skinner born in WI Juneau (in City of Elroy acc'd'g to family source)
POSSIBLE MATCHES in Wisconsin Pre-1907 Vital Records:
Skinner, Unnamed Male born Jan 26 1894 in Juneau County
Skinner, James born Sep 29 1894 in Juneau County
1894 "Mrs Arthur E Skinner" died 1894 Oct 01 in Juneau County, WI
1900 Arthur, Della (2nd wife) & Alfred enumerated in WI Juneau Elroy
1905 [?/Possible] Arthur SKINNER, nephew living with Martin & Kate CROTTY in WI Douglas Superior
1916 [?/Possible] La Crosse Tribune Mar 7 1916: Alfred Skinner of Superior, who has been staying at the Home hotel is quite ill. He has not been able to return to his home.
1916 McKnight Maedella Miss, county school tchr, bds 1700 Herring av in Waco Texas City Directory p334
1918 [?/Possible] La Crosse Tribune and Leader Press Nov 13 1918: Roll of Honor, Section Two. Wounded Slightly ... Alfred A. Skinner, Schofield, Wis. [Note: Schofield is in Marathon County, Wisconsin]
1919 married1 Madella or Maedella or Della Mcknight
1919 Skinner Alf A (Maedella) rms 1700 Herring av (in 1919 Waco City Directory p433)
1919 son Alfred James Skinner born 1919 Nov 05 in McLennan County, TX (birth cert 56033)
1920 Alfred, Della and Alfred J enumerated in TX Kendall Boerne (no occupation for Alfred Sr.)
[1921 NOT listed in Waco City Directory]
c1923 dau Sylvia Margaret SKINNER born 1922 Oct 20 in McLennan County, TX
c1923-1930 Alfred & Madella divorced
1926 Skinner Maedella Mrs bkpr Waco Fuel & Grain Co h1700 Herring av (1926 Waco City Directory p464)
1929 Skinner Madella M (wid A A) r 1818 Arizona av in Dallas TX City Directory p1711
1930 Madella (divorced), Alfred J., Sylvia M. enumerated in TX McLennan Waco, 1104 Alexander
1930 Skinner Maedella Mrs bookkeeper Wco Fuel & Grain Co r 1604 Alexander av (1930 Waco TX City Directory p379)
1943 Alfred James SKINNER reported on a Utah Military record that his mother's name was "Maedella Mcknight Lorenson" (Utah; Military Service Cards, ca. 1898-1975)
1948 [?/POSSIBLE] (acc'd'g to your post in SKINNER surname message board, Alfred resided in/near Wenauchee WA around 1948)
1999 Alfred James SKINNER died 17 Nov 1999 (last residence SLC SaltLake UT)