I think I have it figured out; Catherine E. Cowburn died 4-7-1917 and was the wife of Frederick W. Cowburn Sr. He must have married her after the death of Rosina in 1912 and married Minnie after Catherine. Catherine's maiden name was Whitehair; she was 32 and living with her parents in 1910.
Chicago Tribune (IL)
AGED MEN ENDS HIS LIFE BY JUMPING INTO LAKE.
W. E. Whitehair Leaves Message to Plasterers' Union Declaring He had Gone Crazy -- Girl Inhales Gas.
William E. Whitehair, who was 62 years old and lived at 2625 Calumet avenue, committed suicide yesterday by jumping into the lake at the foot of East Fifty-first street. He was separated from his wife, who has been living at the home of a daughter, Mrs. F. Cowburn, 5038 Jefferson avenue.
Whitehair left a note asking that Mrs. Cowburn be notified, and a postal card addressed to "The Plasterers' union, care of J. Donlin." On the back of this was written: "Sorry, John, but I have gone crazy." The body was recovered.
Copyright 1913, Chicago Tribune. For permission to reprint, contact Chicago Tribune.
Record Number: 19130808ob009
Chicago Tribune (IL)
Margaret Whitehair, March 27, 1916, at the residence of her daughter, Mrs. Frederick W. Cowburn, 5039 Harper-av. Funeral Wednesday at 2 p.m. Interment at Oakwoods cemetery.
Copyright 1916, Chicago Tribune. For permission to reprint, contact Chicago Tribune.
Record Number: 19160328dn037
Since Frederick W. Cowburn Jr. died in 1904, this must be the wife of Frederick Sr.Fred Sr. lived at the above address on Harper in the 1920 census with Minnie and 3 of the younger children. Do you have that? I can post it, if not.
From the Illinois Death Index:
Cowburn, Fred W.d. 8-22-1904aged 24 Chicago, Cook Co.
Rosinad. 6-11-1912aged 52""
Catherine E. d. 4-7-1917""
Frederick W. d. 5-28-1932""
Ruby M. [Walter] d. 5-28-1942 aged 54""
Charles R.d. 11-27-1945""
Fred Sr., Rosina and Fred Jr. came to the U.S. on the SS England, 2 May 1882. Fred Sr. was 24, Rose 23 and Fred Jr. is just shown as an infant.
Mt. Greenwood Cemetery Assn.
2900 W. 111th St.
Chicago, IL 60655-2242
Chicago Tribune (IL)
Charles R. Cowburn of 8235 S. Laflin street, husband of Lillie, nee Thomsen; father of Mrs. Betty Etter, grandfather of Richard Etter, brother of Mary Large, Alice Paul, Walter and Arthur Cowburn. Member of Englewood lodge, No. 653, K. of P. At chapel, 1648 W. 63d street, until Friday noon. Services 2:30 p.m., Friday at Drexel Park Presbyterian church. Interment Evergreen.
Copyright 1945, Chicago Tribune. For permission to reprint, contact Chicago Tribune.
Record Number: 19451129dn111
You may already have this bio from the "History of Illinois and Her People" Chicago American Historical Society 1927:
Walter Cowburn, state's attorney of Mason County, is one of the able attorneys and fearless public officials of this region. He is intensively combative, and never runs away from a fight. His many notable achievements in grappling with organized crime and political protectors of organized criminals have made his name a terror to evil doers. No power on earth can swerve Walter Cowburn from doing his duty according to the dictates of his conscience, for the dominant quality of the man is his independence.
The birth of Mr. Cowburn occurred at Chicago, in a house standing at the intersection of Huron and Cass streets, in one of the fine residential districts of that city, January 28, 1885. His father, Frederick W. Cowburn, was a contractor and builder, and had settled at Chicago when he came to the United States from Leeds, England, in 1878. Selecting the North Side of the present metropolis, Frederick W. Cowburn was connected with its development during a period of forty years, but is now living retired from his former activities. He was married in England to Rose Simpson, whose death occurred in 1912. She bore him eight children, six of whom survive: Mrs. George Scott, of Circle, Montana; Walter, whose name heads this review; Mary, who is married; Charles R., who is with the Bell Telephone Company of Chicago; Arthur, who is in the employ of the Bell Telephone Company at Chicago; and Alice, who is with her father.
Walter Cowburn did his school work in the grade and high schools of Chicago and was graduated from the Hyde Park High School. When only 16 years old, he left home and began working for the Western Telegraph Company, and was first in the operating room and later in the traffic department, and when he left that company he went to the Bell Telephone Company. When he left the latter in 1916, he was city night wireman.
In the meanwhile he had been studying law, and entering the Hamilton College of Law, Chicago, he was graduated from it in June, 1916, and was admitted to the bar before the Supreme Court of Illinois. Beginning his practice at Chicago, Mr. Cowburn became associated with the Utilities Indemnity Exchange of that city as a member of it's legal department. After two years association with the exchange, he formed an association with Frank B. Teed, assistant attorney general of Illinois. This connection was maintained until he came to Mason City.
Upon coming to Mason City Mr. Cowburn took charge of the local office of the firm of Lucas & Schradzki, one of the strongest legal firms of Mason County. When Mr. Lucas resigned as state's attorney of Mason County, Mr. Cowburn was appointed to succeed him, and is making a splendid record in that office.
During the late war he tried to enlist, but was refused on account of a physical defect, but he was registered. He was a member of the American Protective League, an auxiliary of the United States Department of Justice. High in Masonry, Mr. Cowburn belongs to Lodge Number 758, A.F. and A.M., of Chicago, and to Oriental Consistory, Chicago.
On June 11, 1906, Mr. Cowburn married Miss Ruby Whimsett, a daughter of William George and Elizabeth [Chatterton] Whimsett. Mrs. Cowburn was born at Coburg, Ontario, Canada, but she was reared at Chicago, where her father was a business man. She was graduated from the Hyde Park High School, and is third in the family of four children born to her parents. Mr. and Mrs. Cowburn have a daughter, Marie, who is a high school student of Chicago.
I thought this was really good as it gives Rose Cowburn's maiden name!
Hope this is helpful,