I am sure she is related, but I don't know how.I have never seen Louise's name in the census for Joliet.If I knew her parents, I could almost certainly tell you our connection.
Charles Johnson, who you say was married to Louise, was interred in the Van Allen plot in Oakwood Cemetery, Joliet, IL on 09/02/1886.
Those who are buried there in lot 53, block M are:
interrment date: Mrs. Charles Van Allen,07/03/1879 Child of Charles08/26/1879 Alex Van Allen08/30/1911 Charles Johnson09/02/1886 Charles F. Van Allen02/03/1889 Hiram Van Allen07/02/1893 Pauline Murphy03/06/1897 Eliza Van Allen03/25/1898 John D. Van Allen12/31/1904
Charles F. Van Allen, Pauline, Alex (my gg grandfather) and John D. Van Allen were all children of Hiram Van Allen and Eliza Hildreth.The only stone on the plot is for John D. Van Allen, who served in the 20th IL infantry during the Civil War.The information above came from the Oakwood Cemetery sexton.
If Louise was born in 1870, I'd say she has to be a child of one of Hiram's children.Do you know anything more than what you have already told me?
I'm eager to see what our connection is, so please e-mail me at firstname.lastname@example.org.