I hope you've looked at the wonderful research Taryn provided you.It appears the the references to your family in records are scant.I checked for a marriage in the online Grand Forks county marriage license search, and at in Minnesota records www.mncounty.com, and the pre-1900 marriage database for St. Louis County, Minnesota at www.genweb.com and didn't find one for a Mary & Wallace Forkey.
There is one child who may be a Forkey in the records of the Memorial Park Cemetery in Grand Forks, North Dakota.I mention it because in the 1900 census Mary is recorded as the mother of 3 of which 2 are living. The name is entered 2 ways so there may be an interpretation issue:
Forhey or Forker, Sam (child or infant) d. 10 Jan 1895 buried 10 Jan 1895 in Old Add. Blk 266, Lot 1 or Lot 2, grave 13
Chronicling America is the website that contains scans of newspapers and is free to view.There are 7 mentions of Forkey published in the Bemidji Pioneer.One mentions Mary Forkey and the others deal with Wallace and the daughter Lily/Lillie/Lilly.I'm pasting in the web addresses and I hope that you will be able to take a look at them.
Regarding Lillie there are a couple of mentions of a Lillie Forkey who married a Walter Adamski in 1914 at www.genealogybank.com, another newspaper site.The paper these 2 references were published in is the Duluth News-Tribune.The first is dated 25 Dec 1910 (no page # given) but mentions Walter Adamski and Lillie Forkey both of St. Louis County, received a marriage license.The second article is dated 12 Mar 1914 and says in snippet form "For more than three years a marriage license issued to Walter Adamski and Lillie Forkey has been unused by Adamski.Yesterday it was produced and the couple, presenting it to Judge S.W. Gilpin of the probate court were...." You may have to go sideways a bit and look for Lily, particularly if she is a full sister to your dad Wallace.
Both of your father Wallace's draft registrations are included at www.familysearch.org.In each of the 1942 WWII and the WWI his birthplace is recorded as East Grand Forks, Minnesota.East Grand Forks is just east of Grand Forks, North Dakota on the Minnesota side of the Red River of the North.In WWI, his address is given as Superior Wisconsin and his place of employment is the State Hospital of North Dakota at Jamestown.
The devil is in detail--although very little appears to pertain to Mary, the person you are seeking, perhaps there is a clue in some of this stuff that will help you.