If you search on Ancestry's U.S. Public Records Index or Phone & Address Index search, well over 120 entries come up for your surname KNOPF!! (You'll want to take a look!)

Also, when you do a Yahoo People search for KNOPF in Wisconsin, 23 entries come up with that spelling. It surely can't hurt to take a look & see if any of these are close proximity to Rib Lake, WI. Maybe make a few phone calls and/or send out a couple of letters of inquiry. . .

I believe Rib Lake is in Taylor County, and there are afew entries for Hayward, WI, which is in Sawyer County, WI- maybe send a post and/or look up request to the respective Rootsweb County Genealogy web sites and see if there is a response for your surnames.
Also check out Social Security Death Index on Ancestry that lists many, many KNOPF entries for Wisconsin-- including a Fred KNOPF, born 1887 and died 1964 in Wausau, Wisconsin (Marathon County).
Hope this is helpful.