Bio from "Portrait and Biographical Record of Clinton, Washington, Marion, and Jefferson Counties, Illinois", published in 1894 by Chapman Publishing Co., Chicago -- pages 328-331, which include a full page engraving of William M. CASEY, with his signature, and a large biographical article --
"William M. CASEY is a retired farmer of Centralia, and one of the honored early settlers and prominent citizens of Marion County.
William M. CASEY was reared on the old homestead and was educated in a log schoolhouse with a puncheon floor, slab seats and greased paper windows. The history of pioneer life is familiar to him, not from hearsay, but from experience. In 1852 he married Julia E. KENNEDY, and they had three children. After his marriage Mr. CASEY located in Jefferson, and 4 years later removed to Washington County, where for 10 years he owned and operated a farm of 240 acres. He then sold the property and came to Centralia, where he has since lived in retirement from active labor.
Mr. CASEY has been a member of the Methodist Church since the age of nine years, and his wife since twelve years old. He has been numbered among its officers for 38 years, and has ever been prominent in its work. He cast his first Presidential vote for Zachary Taylor, and was a Whig until 1856, since which time he has been a stanch Republican. For ten years he served as Township Treasurer of Washington, but has never been an office seeker. He is now (1894, almost 69 years old) practically living retired, but is still a Director of the Old National Bank, Centralia Mining and Manufacturing Company, and the Centralia Fair Association. He is a worthy representative of one of the prominent families of the state, and his honorable, upright life gives him a leading place among the best citizens of the community."

Obit from the Mt. Vernon Register News, March 8, 1898:
William M. Casey died at his home in Centralia shortly after 5 o'clock yesterday afternoon, aged 72 years. He was, next to Clinton M. Casey, the oldest of four brothers and his death is the first that takes place of the four.
Deceased was born at the parental home, four miles north the the city, on the place now owned by Sylvanus Foster and lived there until a young man. When about 30 years of age he went to Washington county and lived there ten or twelve years, removing thence to Centralia and has made his home in that city. He was never a strong man and for several years has been an invalid. The immediate cause of his death is believed to have been diabetes, from which he has been a sufferer for years. Yesterday morning Mr. Abraham Casey fo Larned, Kan. who was visiting relatives in this place, received a telephone message from Centralia that his brother's condition was most critical and requesting him to come at once to his bedside. He left on Air Line train yesterday, and in a message from him later in the day informed the relatives here that there was but little hope of the invalid's recovery. The deceased leaves a wife and son, Dempey Casey of Centralia, and three brothers, Clinton M. Casey of Pleasant Grove; Abraham M. Casey of Larned, Kan., and W. Barg Casey of this city. The latter, with other relatives from here, will attend the funeral at Centralia tomorrow afternoon at 1 o'clock.

The Elmwood (Centralia, IL) Cemetery records show William M. Casey is buried there, Lot 18 Range 18 Grave 3. Born 12-15-1825, died 3-7-1898.
Also, Dempsey Casey Lot 18 Range 18 Grave 1
Mary H. Grave 2
William M. Grave 3
Alice Grave 4
Imogene Church-Casey buried Lot 18 Range 19 Grave 8