I found this completely by accident:
Mr. Adolphus Busch, of the Anheuser-Busch Brewing Company, has bought the interest originally held by Mr. Ellis Wainwright in the St. Louis Athletic Association. Mr. Wainwright is therefore no longer in any way connected with the Union Club.-St. Louis Globe-Democrat, April 11, 1884
There I was, minding my own business and researching something totally unrelated, when my eyes caught the words "Adolphus Busch" and I stopped to read. Lo and behold, I found something that killed two birds with one stone. We can now say that Wainwright, while an original investor in the Maroons, was bought out in April of 1884. We can also say that Adolphus Busch (pictured above) was an investor in the Maroons and that the brewing family has a history in St. Louis baseball that began eighty years before August Busch, Jr. bought the Cardinals in 1953.