The humorist who encouraged Mark Twain to write the Jumping Frog story was Artemus Ward. Ward, the pen name of Charles Farrar Browne, asked Twain to contribute a tale for an upcoming book.
Twain initially struggled with the assignment and drafted versions that did not fully develop the jumping-frog contest. By the time he produced a version he liked, Ward's book was nearly ready, so Ward sent the story to The New York Saturday Press instead. It appeared on November 18, 1865, under the title “Jim Smiley and His Jumping Frog.”
The story became Twain's first major literary success and was later republished as “The Celebrated Jumping Frog of Calaveras County.” A common mix-up is to credit Bret Harte with commissioning it: Harte later published a revised version in The Californian, helping spread the story, but Artemus Ward was the humorist who originally prompted Twain to write it.