The first "columnist" might have been Bert L. Taylor (B. L. T.), who wrote the "Line 'o Type" column in the Chicago Tribune. "Colyumist" was popular from 1910-1930.
(Oxford English Dictionary)
One who writes a 'column' in the newspaper press (see COLUMN n. 4). In the U.S. sometimes with the jocular spelling colyumist (kljmst).
1920 Blackw. Mag. Aug. 146/1 The 'colyumist' of a New York paper. 1925 Lit. Digest (N.Y.) 27 June 27/2 Here is a Vashti leading the opprest columnist into the promised land of intellectual liberty.
Franklin Pierce Adams (November 15, 1881 — March 23, 1960), was an American columnist (under the pen name F.P.A.), writer, and wit, part of the famous Algonquin Round Table of the 1920s and 1930s.
Born in Chicago, Illinois, he was the son of Moses and Clara (Schlossberg) Adams. He graduated from the Armour Scientific Academy in 1889 and attended the University of Michigan for one year. He first worked for the Chicago Journal in 1903 but soon moved to the New York Evening Mail, where he worked from 1904 to 1913 and began the famed column which would later be known as "The Conning Tower". In 1913, he moved his column to the New York Tribune, where it would take "The Conning Tower" name, staying there until 1921. During his time on the Evening Mail he wrote what remains his best known work, Baseball's Sad Lexicon, a tribute to the Chicago Cubs double play combination of "Tinker and Evers and Chance."
During World War I, Adams was in the U.S. Army, working on the Stars and Stripes, where he would work with Harold Ross, Alexander Woollcott, and other literary lights of the 1920s. After the war, Adams returned to New York. He went to the New York World, in 1921, writing there until that paper closed in 1931. He returned to his old paper, renamed the New York Herald Tribune, staying until 1937 when he went to the New York Post. He ended his column in September 1941.
2 December 1911, Chicago Daily Tribune, "A Line-o'-Type or Two" by B.L.T., pg. 10:
("Colyumist" is somewhere here -- ed.)
17 November 1912, Atlanta Constitution, pg. E3:
Fire Away, Colyumists
17 February 1916, The Dial, pg. 157:
THE PRINCE OF "COLYUMISTS."
But some forty-five years ago a professor of mathematics in London, Augustus De Morgan, was doing precisely the same sort of thing in "The Athenaeum," under the title, "A Budget of Paradoxes," that F. P. A., B. L. T., an a few others are doing now in our metropolitan newspapers.
3 April 1916, Lincoln (NE) Daily News, pg. 9:
Jay E. House, colyumist, mayor and baseball writer for Topeka cast his raw beef with regularity if one can judge from his comments on the national sport.
14 October 1916, Puck, pg. 14:
The Diary of a Rising Young Colyumist.
18 May 1920, Olean (NY) Evening Herald, pg. 2:
"Free verse" has been the rage, for the last few years, among a certain class of literary dilettantes, but it has failed to make any impression on the general reading public. Why? The answer, perhaps, is found in a little poem by "F.P.A.," the famous "colyumist" of the New York Tribune, in a recently published volume of verse.