I am a volunteer researcher for Decatur County; this family is not in my ancestorial line. Found in Mt. Aerie Cemetery in Sand Creek Twp: James W. Armstrong - Nov. 24, 1841 - Oct 5, 1909with Helen E., his wife - d. Apr. 11, 1895aged 27yr, 1mo, 7 da.
In the same cemetery - second wife: Euphamie Davis Armstrong -1853 - 1936
James wife Helen E. apparently went by the name of Ella, as she was found in the Dec. Co. death records index: Ella Armstrong - married, b. Sandcreek Twp; d. 4/11/1895 in Letts Corner; age 28; Father: Elgie Tanner; Mother: Sarah A. Stout, b. Franklin Co., IN.
James W. Armstrong m. Helen E. Tanner on 26 Aug, 1888 - record appears in Book M, page 441 of the office of Clerk of the Circuit Court in Greensburg. James W. Armstrong m. Euphamie Davis on 11 Jun, 1896 - book O (as in 'oh' not zero) page 36.
The book - History of Decatur County - by Lewis Harding, 1915 has a biography on an Alfred M. Armstrong.It lists Alfred's parents as Robert and Rebecca Jane (Hamilton) Armstrong and having the following children: James W., John H., Oliver P.(living in Fayette Co. Il when bio. was written), George W., Albert M., and Francis D. Robert Armstrong was a native of Pennsylvania, born in 1817 and came to Decatur Co. with his parents when he was 3 yrs old.He married Rebecca Jane Hamilton, who was born in 1818, who was the daughter of James Hamilton. Robert was a charter member of the Free and Accepted Masons at Westport.He died in 1878.Robert's siblings were: James, William, Mrs. Sallie Barnes, Mrs. Jane Singleton, Mrs. Mary Falkenberg, Eliz. Longnecker, and Mrs. Rebecca Boicourt. Rebecca died and Robert married Eliza Jane McDonald and they had three children - Robert F., Mrs. Mary Jane Harding, and Mrs. Louisa Helen Updike.
Robert and Rebecca are buried in Horse Shoe Bend Cemetery in Sandcreek Twp: Robert - d. Dec 17, 1876A. 60y, 2mo, 28da. Rebecca J., wife - d. Jan 3, 1856,A. 33y, 11m. 9da. Robert's brother James & wife, sister Rebecca Boicourt & husb., brother William, sister Eliz. Longnecker & husb. are all buried in that cemetery.
Robert's second wife, Eliza, is buried in Mt. Aerie Cemetery - Mar 23, 1836 - Apr. 3, 1910.
I hope that some of this helps! Good luck in your continued research!