Late in 19th century America, comic strips began to appear in the Sunday supplements of newspapers. The first among these comic strips was 1896's The Yellow Kid, considered the 1st comic strip
Richard Felton Outcault's The Yellow Kid which appeared in the February 16, 1896 Hearst New York American. In March 1897, these strips were compiled into Hearst's Sunday Journal and and sold for 5 cents. From this humble beginning an industry was born, though it would not have immediate success.
From this time through the early 1930's, many publishers produced cartoon books for the public, including many promotion comics. Though many of these companies quickly vanished, their characters remain to this day and are among the most well known, including Little Orphan Annie, Dick Tracy, Popeye, Mutt & Jeff, Little Nemo, and Buster Brown. It was also during this time that one of the earliest "funny animals" Krazy Kat, first appeared. In 1910 George Herriman began featuring Krazy Kat in his daily newspaper in "The Family Upstairs" strip. By 1916 Krazy Kat was starring in his own color Sunday strip. 
Early commercial attempts...
In January 1929 George Delacorte, working for pulp publisher New Fiction Company, published The Funnies No. 1, the first four-color comic newsstand publication, featuring original comic pages and a cover price of 10 cents. Until No. 5, it was a weekly publication the same size as the free Sunday supplements, making confusion easy and ensuring it's failure. In an attempt to save the publication, Delacarte reduced the price to 5 cents with No. 25, however The Funnies ceased publication with No.36. Among The Funnies historic firsts was the publication of work by Victoria Pazmino, the first published female comic book artist.
More strips debut...
Birth of the modern comic...
newspaper reprints including Mutt and Jeff, Joe Palooka, and Reg'lar Fellas, they created Funnies on Parade. This was the first comic produced in a format similiar to modern comics. Looking to test their product, they published 10,000 copies to be given out as premiums by Proctor and Gamble.
Impressed by this success, Gaines convinced Eastern Color that he could sell thousands of these to big advertisers like Kinney Shoe Stores, Canada Dry, and Wheatena to be used as premiums and radio giveaways. Because of this, Eastern followed by printing Famous Funnies: A Carnival of Comics and later Century of Comics, both containing Sunday newspaper reprints. M. C. Gaines was able to sell these in quantities of 100,000 to 250,000 copies. Century of Comics was the 2nd comic book and the first 100 page comic.
Commercial success at last...
With these enormous successes behind him and seeing the "Big Little Books" that were so popular at the time, Gaines decided to try another test, actually trying to *SELL* these books. Taking a few extra giveaway books, he marked them with a 10 cent price tag and proceeded to distribute them to area newsstands on a Friday. When he returned on Monday, every copy had sold!
Shortly after this saw the publication of the first four color comic featuring just a single character. Gaines, looking for more promotions, approached and convinced the sponsers of the Skippy radio show to publish a comic based on the character. With their backing, 500,000 copies of Skippy's Own book of Comics were printed. The book was advertised on the air and given away in drug stores to anyone who bought a tube of Phillip's toothpaste.
Even more strips debut...
During this time more now classic comic strips began to appear. While working on the Secret Agent X-9 strip, Alex Raymond developed an idea for a science fiction strip. Shortly thereafter, in January 1934, the first Flash Gordon strips saw publication. Later, after creating an additional strip, Jungle Jim, to go along with his increasingly popular Flash Gordon, Raymond left Secret Agent X-9. Flash Gordon's popularity continued to grow, with Flash Gordon related merchandise soon flooding the stores and a weekly radio show was being aired. In 1936 a Flash Gordon serial starring Buster Crabbe was produced by Universal. At the time is was the most expensive serial ever made. Near the close of the year, on October 19, 1934, Milton Canniff's Terry and the Pirates made their debut in the Tribune-News Syndicate. Terry and the infamous The Dragon Lady continue to endure to this day.