Lutheran baptism record in Germany lists his parents as Jacob Kaerath and Caroline Kroll Prill, and lists his name as Rudolf Albert Carl Kaerath.
Nickname was "Red', based on his hair color.
They came from west Prussia and all the records were destroyed in the two wars. They were originally from near Danzig (now Gdansk), a town called Brumberg. He was the last survivor of 13 children.
He was a character in the larger sense as he was a Mississippi River boat captain. He was quite a drinker and a gambler.
Listed with his wife and son Martin in 1900 Wisconsin census as a corker (25, GER), married 1 yr. It shows him as having immigrated in 1880, 20 yrs in the US and naturalized.
He is listed as a ship's carpenter (30, GER) in the 1905 Wisconsin state census, with his wife plus sons Martin and George.
Listed in 1910 as a boat Pilot (35, GER) with his wife of 11 yrs, Ida (30, GER) and children Martin R. (10, WI), George P. (6, WI), and Walter H. (1, WI). It says he immigrated in 1880 from Germany and was naturalized in 1895.
In 1920 he was master pilot of a Government boat, with 4 sons and 2 daughters. His pilots license went from St. Paul to St. Louis although he was up and down the Mississippi all the time. He worked for the Federal Barge line.
In 1930 he is listed as a navigation Pilot with his wife, 2 sons and 2 daughters.
They are listed as only Rudolph (65) and Ida (60) in 1940 and again in 1950.

Society Page of Winona (Minn.) Republican Herald - 12 Feb 1949:
Friends Hail Karnaths on Golden Anniversary
Captain and Mrs R. J. Karnath, Fountain City, Wis. observed their 50th wedding anniversary Friday at services and a family dinner at St. Michael's Lutheran church where they were married February 11, 1899, and an open house at their home. All their children, grandchildren and only great-grandchild with the exception of two grandchildren, were present for the celebration as were two of the attendants of 50 years ago, Mrs Emma Rosenow, Hammond, Ind., and Mrs Gerhardt Westerkamp, Fountain City.
Gifts, flowers and cards of congratulation poured in on Captain and Mrs R. J. Karnath, Fountain City, to mark their golden wedding anniversary Friday, including cards and flowers from the engineers and firemen on the trains which pass the Karnath family home near the railroad track here, and with whom Captain and Mrs Karnath have maintained a "waving" friendship since childhood.
Captain and Mrs Karnath's anniversary celebration was highlighted also by the return of all their children to the family home, including Mrs Byron (Vida) Armstrong with her husband, Captain Armstrong and their three children. Captain and Mrs Armstrong are en route from Trinidad, BVI where he was stationed with the U. S. Army Air Force for the past two years, to McGuire Field, NJ.
The anniversary day also was the birthday of Captain Karnath and of their oldest daughter, Mrs Elmer (Beata) Loken, and proved to be the baptismal day of their new granddaughter, Nancy Kay Armstrong, seven month old daughter of Captain and Mrs Armstrong, who was baptized following special services held at St Michael’s Lutheran church Friday at 5 PM in honor of Captain and Mrs Karnath.
The services for Captain and Mrs Karnath and the baptism were conducted by the Rev. Herbert Nommensen. Mrs Armstrong sang "I Love Thee" and Mrs Loken, "Bless This House." Two of the attendants at the original wedding were present, Mrs Emma Rosenow, Hammond, Ind, sister of Mrs Karnath and Mrs Gerhardt Westerkamp, Fountain City, Wis. The other attendants, Leonard Bensel, brother of Mrs Karnath, and Mr Westerkamp, are both dead.
A family dinner was served in the church social rooms for 40 guests by the Ladies Aid of the church of which Mrs Karnath has been a member for 51 years. Jonquils and yellow pompoms and tapers centered the table which was arranged in a U shape. The anniversary cake was placed in front of the couple and the birthday cakes for Captain Karnath and Mrs Loken were on the side tables. Open house for about 100 guests was held at the home from 7 to 10 PM Captain and Mrs Karnath have always lived their entire married life in the same home, and since children waved at the railroad men operating trains thru Fountain City, the friendship with the crews has grown, and is now an even more important activity since Captain Karnath's retirement.
Captain and Mrs Karnath were both born in West Prussia, Germany, the former February 11, 1875. He was the son of Mr and Mrs Jacob (Caroline) Karnath and was 74 years old Friday. Mrs Karnath, the former Ida Bensel, daughter of Mr and Mrs August Bensel, was born July 10, 1879. They came to Fountain City with their parents from Germany in the 1880's.
The couple was married at St Michael's Lutheran church, Fountain City February 11, 1899.
Captain Karnath retired from active United States government service on the upper Mississippi in November, 1941, after nearly a half century in the service. He engaged in logging on the river before he became a flunky helping with the cooking on an upper river boat operating between Red Wing and Fountain City in 1891. Later he worked as a deckhand before entering the government service in 1892.
He started work for the government on boats between St Paul and Rock Island as a deckhand, watchman, fireman and mate. He received his pilot's license about 42 years ago, and served as a captain from that time until he made his last trip as captain on the General Allen in June 1941. He worked in the government boat yards from June to November of that year before officially retiring.
Boats he captained were engaged in general government work, clearing the channel, towing brush and rock and towing dam equipment and coal. They included the Elsie, Ada, Alert, Fury, Coal Bluff, Ellen, Elinor and General Allen. He was captain of the Coal Bluff that brought up the first coal tow, and experimental tow from the Dubuque to Fountain City about 37 years ago.
Twice the Ellen sank while he was operating it, both times when it hit a snag. The Ellen also was the boat he captained when a record tow of 42 barges of dam equipment , one of the largest on the upper river, was made. The Ellen picked up equipment from Fountain City on down the river.
Three of his sons hold pilot's licenses, Captain Walter Karnath, Winona, master pilot of the Alexander MacKenzie of the Central Barge Company, operating on the Illinois and Mississippi rivers up to St Paul; Captain George Karnath, Rock Island , IL, master pilot of the Cairo of the Federal Barge Line, and Rudolf, Minneapolis, who was forced to retire from his position as pilot on the river because of his health.
The couple has another son, Martin, Portland, OR, who is battalion chief in the fire department, their two daughters, 13 grandchildren and one great-grandchild. All the children, their wives and husbands, all the grandchildren except Jack Karnath, son of Captain and Mrs George Karnath, who is stationed with the Army Air Force at Lackland Field, Texas, and Mrs Robert Fasset, Portland, and their great-grandchild were present at the celebration.
Captain Karnath is the last of a family of 13 children. Mrs Karnath has two sisters, Mrs Rosenow, Hammond, and Mrs Samuel Goetz, Chicago, who were both here for the celebration. The latter was accompanied by her daughter Sophie.
Other guests from out-of-town were Mr and Mrs Martin Karnath and their grandchild, Craig Fasset, the only great-grandchild of Captain and Mrs George Karnath, Portland; Captain and Mrs George Karnath and daughter Judy, Rock Island; Dr and Mrs Loken and daughter Karen and son Michael, Le Sueur, MN; Captain and Mrs Walter Karnath and children James, Richard, Jean and Ruth Ann, Winona; Mr and Mrs Rudolf Karnath and daughter Bette, Minneapolis; Captain and Mrs Armstrong and children Kathleen, Keith and Nancy Kay; and Mrs R. J. Starbeck, Minneapolis.
[Obituary] The Winona Daily News - Thursday, 8 June 1961, pg 15
Capt. R. J. Karnath
FOUNTAIN CITY, Wis. (Special) Capt. Rudolph J. Karnath, about 85, a retired river captain, died unexpectedly at his home in Fountain City early this morning. He had been in poor health for some time. Among his survivors is a son, Walter, Winona. Colby Funeral Home here has charge of funeral arrangements, which are incomplete, pending word from relatives. Services will be held either Saturday or Monday.