Just found an early story by Youmans, published by the McClure Syndicate in 1910, titled "Hearts By Freight." No dogs or cats--just freight trains, hobos, and illicit love. Read it here, compliments of Google News. The tale seems to have first appeared in Pittsburgh Daily Sun on 5 May 1910, and the image to the left is from a reprint in the 8 Dec. 1910 issue of New Oxford Item, page 2. This story predates her 1921 "The Man Who Wanted A Dog That Would Kill."Youmans has this to say about the appearance of her first short story:
"I claim the world's record for length of time in writing, more or less steadily, before I saw anything of mine in print. From the time I wrote, copied and bound my first MS, 1884 [at the age of 6], announcing my literary aspiration, until my first storiette, 'Hearts by Freight' was printed...was exactly twenty-six years--twice as long as Hergesheimer's historical apprenticeship."